Provided by: libunicode-collate-perl_1.27-1_amd64 bug

NAME

       Unicode::Collate - Unicode Collation Algorithm

SYNOPSIS

         use Unicode::Collate;

         #construct
         $Collator = Unicode::Collate->new(%tailoring);

         #sort
         @sorted = $Collator->sort(@not_sorted);

         #compare
         $result = $Collator->cmp($a, $b); # returns 1, 0, or -1.

       Note: Strings in @not_sorted, $a and $b are interpreted according to Perl's Unicode
       support. See perlunicode, perluniintro, perlunitut, perlunifaq, utf8.  Otherwise you can
       use "preprocess" or should decode them before.

DESCRIPTION

       This module is an implementation of Unicode Technical Standard #10 (a.k.a. UTS #10) -
       Unicode Collation Algorithm (a.k.a. UCA).

   Constructor and Tailoring
       The "new" method returns a collator object. If new() is called with no parameters, the
       collator should do the default collation.

          $Collator = Unicode::Collate->new(
             UCA_Version => $UCA_Version,
             alternate => $alternate, # alias for 'variable'
             backwards => $levelNumber, # or \@levelNumbers
             entry => $element,
             hangul_terminator => $term_primary_weight,
             highestFFFF => $bool,
             identical => $bool,
             ignoreName => qr/$ignoreName/,
             ignoreChar => qr/$ignoreChar/,
             ignore_level2 => $bool,
             katakana_before_hiragana => $bool,
             level => $collationLevel,
             long_contraction => $bool,
             minimalFFFE => $bool,
             normalization  => $normalization_form,
             overrideCJK => \&overrideCJK,
             overrideHangul => \&overrideHangul,
             preprocess => \&preprocess,
             rearrange => \@charList,
             rewrite => \&rewrite,
             suppress => \@charList,
             table => $filename,
             undefName => qr/$undefName/,
             undefChar => qr/$undefChar/,
             upper_before_lower => $bool,
             variable => $variable,
          );

       UCA_Version
           If the revision (previously "tracking version") number of UCA is given, behavior of
           that revision is emulated on collating.  If omitted, the return value of
           "UCA_Version()" is used.

           The following revisions are supported.  The default is 36.

                UCA       Unicode Standard         DUCET (@version)
              -------------------------------------------------------
                 8              3.1                3.0.1 (3.0.1d9)
                 9     3.1 with Corrigendum 3      3.1.1 (3.1.1)
                11              4.0                4.0.0 (4.0.0)
                14             4.1.0               4.1.0 (4.1.0)
                16              5.0                5.0.0 (5.0.0)
                18             5.1.0               5.1.0 (5.1.0)
                20             5.2.0               5.2.0 (5.2.0)
                22             6.0.0               6.0.0 (6.0.0)
                24             6.1.0               6.1.0 (6.1.0)
                26             6.2.0               6.2.0 (6.2.0)
                28             6.3.0               6.3.0 (6.3.0)
                30             7.0.0               7.0.0 (7.0.0)
                32             8.0.0               8.0.0 (8.0.0)
                34             9.0.0               9.0.0 (9.0.0)
                36            10.0.0              10.0.0(10.0.0)

           * See below for "long_contraction" with "UCA_Version" 22 and 24.

           * Noncharacters (e.g. U+FFFF) are not ignored, and can be overridden since
           "UCA_Version" 22.

           * Out-of-range codepoints (greater than U+10FFFF) are not ignored, and can be
           overridden since "UCA_Version" 22.

           * Fully ignorable characters were ignored, and would not interrupt contractions with
           "UCA_Version" 9 and 11.

           * Treatment of ignorables after variables and some behaviors were changed at
           "UCA_Version" 9.

           * Characters regarded as CJK unified ideographs (cf. "overrideCJK") depend on
           "UCA_Version".

           * Many hangul jamo are assigned at "UCA_Version" 20, that will affect
           "hangul_terminator".

       alternate
           -- see 3.2.2 Alternate Weighting, version 8 of UTS #10

           For backward compatibility, "alternate" (old name) can be used as an alias for
           "variable".

       backwards
           -- see 3.4 Backward Accents, UTS #10.

                backwards => $levelNumber or \@levelNumbers

           Weights in reverse order; ex. level 2 (diacritic ordering) in French.  If omitted (or
           $levelNumber is "undef" or "\@levelNumbers" is "[]"), forwards at all the levels.

       entry
           -- see 5 Tailoring; 9.1 Allkeys File Format, UTS #10.

           If the same character (or a sequence of characters) exists in the collation element
           table through "table", mapping to collation elements is overridden.  If it does not
           exist, the mapping is defined additionally.

               entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
           0063 0068 ; [.0E6A.0020.0002.0063] # ch
           0043 0068 ; [.0E6A.0020.0007.0043] # Ch
           0043 0048 ; [.0E6A.0020.0008.0043] # CH
           006C 006C ; [.0F4C.0020.0002.006C] # ll
           004C 006C ; [.0F4C.0020.0007.004C] # Ll
           004C 004C ; [.0F4C.0020.0008.004C] # LL
           00F1      ; [.0F7B.0020.0002.00F1] # n-tilde
           006E 0303 ; [.0F7B.0020.0002.00F1] # n-tilde
           00D1      ; [.0F7B.0020.0008.00D1] # N-tilde
           004E 0303 ; [.0F7B.0020.0008.00D1] # N-tilde
           ENTRY

               entry => <<'ENTRY', # for DUCET v4.0.0 (allkeys-4.0.0.txt)
           00E6 ; [.0E33.0020.0002.00E6][.0E8B.0020.0002.00E6] # ae ligature as <a><e>
           00C6 ; [.0E33.0020.0008.00C6][.0E8B.0020.0008.00C6] # AE ligature as <A><E>
           ENTRY

           NOTE: The code point in the UCA file format (before ';') must be a Unicode code point
           (defined as hexadecimal), but not a native code point.  So 0063 must always denote
           "U+0063", but not a character of "\x63".

           Weighting may vary depending on collation element table.  So ensure the weights
           defined in "entry" will be consistent with those in the collation element table loaded
           via "table".

           In DUCET v4.0.0, primary weight of "C" is 0E60 and that of "D" is "0E6D". So setting
           primary weight of "CH" to "0E6A" (as a value between 0E60 and "0E6D") makes ordering
           as "C < CH < D".  Exactly speaking DUCET already has some characters between "C" and
           "D": "small capital C" ("U+1D04") with primary weight 0E64, "c-hook/C-hook"
           ("U+0188/U+0187") with 0E65, and "c-curl" ("U+0255") with 0E69.  Then primary weight
           "0E6A" for "CH" makes "CH" ordered between "c-curl" and "D".

       hangul_terminator
           -- see 7.1.4 Trailing Weights, UTS #10.

           If a true value is given (non-zero but should be positive), it will be added as a
           terminator primary weight to the end of every standard Hangul syllable. Secondary and
           any higher weights for terminator are set to zero.  If the value is false or
           "hangul_terminator" key does not exist, insertion of terminator weights will not be
           performed.

           Boundaries of Hangul syllables are determined according to conjoining Jamo behavior in
           the Unicode Standard and HangulSyllableType.txt.

           Implementation Note: (1) For expansion mapping (Unicode character mapped to a sequence
           of collation elements), a terminator will not be added between collation elements,
           even if Hangul syllable boundary exists there.  Addition of terminator is restricted
           to the next position to the last collation element.

           (2) Non-conjoining Hangul letters (Compatibility Jamo, halfwidth Jamo, and enclosed
           letters) are not automatically terminated with a terminator primary weight.  These
           characters may need terminator included in a collation element table beforehand.

       highestFFFF
           -- see 2.4 Tailored noncharacter weights, UTS #35 (LDML) Part 5: Collation.

           If the parameter is made true, "U+FFFF" has a highest primary weight.  When a boolean
           of "$coll->ge($str, "abc")" and "$coll->le($str, "abc\x{FFFF}")" is true, it is
           expected that $str begins with "abc", or another primary equivalent.  $str may be
           "abcd", "abc012", but should not include "U+FFFF" such as "abc\x{FFFF}xyz".

           "$coll->le($str, "abc\x{FFFF}")" works like "$coll->lt($str, "abd")" almost, but the
           latter has a problem that you should know which letter is next to "c". For a certain
           language where "ch" as the next letter, "abch" is greater than "abc\x{FFFF}", but less
           than "abd".

           Note: This is equivalent to "(entry => 'FFFF ; [.FFFE.0020.0005.FFFF]')".  Any other
           character than "U+FFFF" can be tailored by "entry".

       identical
           -- see A.3 Deterministic Comparison, UTS #10.

           By default, strings whose weights are equal should be equal, even though their code
           points are not equal.  Completely ignorable characters are ignored.

           If the parameter is made true, a final, tie-breaking level is used.  If no difference
           of weights is found after the comparison through all the level specified by "level",
           the comparison with code points will be performed.  For the tie-breaking comparison,
           the sort key has code points of the original string appended.  Completely ignorable
           characters are not ignored.

           If "preprocess" and/or "normalization" is applied, the code points of the string after
           them (in NFD by default) are used.

       ignoreChar
       ignoreName
           -- see 3.6 Variable Weighting, UTS #10.

           Makes the entry in the table completely ignorable; i.e. as if the weights were zero at
           all level.

           Through "ignoreChar", any character matching "qr/$ignoreChar/" will be ignored.
           Through "ignoreName", any character whose name (given in the "table" file as a
           comment) matches "qr/$ignoreName/" will be ignored.

           E.g. when 'a' and 'e' are ignorable, 'element' is equal to 'lament' (or 'lmnt').

       ignore_level2
           -- see 5.1 Parametric Tailoring, UTS #10.

           By default, case-sensitive comparison (that is level 3 difference) won't ignore
           accents (that is level 2 difference).

           If the parameter is made true, accents (and other primary ignorable characters) are
           ignored, even though cases are taken into account.

           NOTE: "level" should be 3 or greater.

       katakana_before_hiragana
           -- see 7.2 Tertiary Weight Table, UTS #10.

           By default, hiragana is before katakana.  If the parameter is made true, this is
           reversed.

           NOTE: This parameter simplemindedly assumes that any hiragana/katakana distinctions
           must occur in level 3, and their weights at level 3 must be same as those mentioned in
           7.3.1, UTS #10.  If you define your collation elements which violate this requirement,
           this parameter does not work validly.

       level
           -- see 4.3 Form Sort Key, UTS #10.

           Set the maximum level.  Any higher levels than the specified one are ignored.

             Level 1: alphabetic ordering
             Level 2: diacritic ordering
             Level 3: case ordering
             Level 4: tie-breaking (e.g. in the case when variable is 'shifted')

             ex.level => 2,

           If omitted, the maximum is the 4th.

           NOTE: The DUCET includes weights over 0xFFFF at the 4th level.  But this module only
           uses weights within 0xFFFF.  When "variable" is 'blanked' or 'non-ignorable' (other
           than 'shifted' and 'shift-trimmed'), the level 4 may be unreliable.

           See also "identical".

       long_contraction
           -- see 3.8.2 Well-Formedness of the DUCET, 4.2 Produce Array, UTS #10.

           If the parameter is made true, for a contraction with three or more characters (here
           nicknamed "long contraction"), initial substrings will be handled.  For example, a
           contraction ABC, where A is a starter, and B and C are non-starters (character with
           non-zero combining character class), will be detected even if there is not AB as a
           contraction.

           Default: Usually false.  If "UCA_Version" is 22 or 24, and the value of
           "long_contraction" is not specified in "new()", a true value is set implicitly.  This
           is a workaround to pass Conformance Tests for Unicode 6.0.0 and 6.1.0.

           "change()" handles "long_contraction" explicitly only.  If "long_contraction" is not
           specified in "change()", even though "UCA_Version" is changed, "long_contraction" will
           not be changed.

           Limitation: Scanning non-starters is one-way (no back tracking).  If AB is found but
           not ABC is not found, other long contraction where the first character is A and the
           second is not B may not be found.

           Under "(normalization => undef)", detection step of discontiguous contractions will be
           skipped.

           Note: The following contractions in DUCET are not considered in steps S2.1.1 to
           S2.1.3, where they are discontiguous.

               0FB2 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC RR)
               0FB3 0F71 0F80 (TIBETAN VOWEL SIGN VOCALIC LL)

           For example "TIBETAN VOWEL SIGN VOCALIC RR" with "COMBINING TILDE OVERLAY" ("U+0344")
           is "0FB2 0344 0F71 0F80" in NFD.  In this case "0FB2 0F80" ("TIBETAN VOWEL SIGN
           VOCALIC R") is detected, instead of "0FB2 0F71 0F80".  Inserted 0344 makes "0FB2 0F71
           0F80" discontiguous and lack of contraction "0FB2 0F71" prohibits "0FB2 0F71 0F80"
           from being detected.

       minimalFFFE
           -- see 1.1.1 U+FFFE, UTS #35 (LDML) Part 5: Collation.

           If the parameter is made true, "U+FFFE" has a minimal primary weight.  The comparison
           between "$a1\x{FFFE}$a2" and "$b1\x{FFFE}$b2" first compares $a1 and $b1 at level 1,
           and then $a2 and $b2 at level 1, as followed.

                   "ab\x{FFFE}a"
                   "Ab\x{FFFE}a"
                   "ab\x{FFFE}c"
                   "Ab\x{FFFE}c"
                   "ab\x{FFFE}xyz"
                   "abc\x{FFFE}def"
                   "abc\x{FFFE}xYz"
                   "aBc\x{FFFE}xyz"
                   "abcX\x{FFFE}def"
                   "abcx\x{FFFE}xyz"
                   "b\x{FFFE}aaa"
                   "bbb\x{FFFE}a"

           Note: This is equivalent to "(entry => 'FFFE ; [.0001.0020.0005.FFFE]')".  Any other
           character than "U+FFFE" can be tailored by "entry".

       normalization
           -- see 4.1 Normalize, UTS #10.

           If specified, strings are normalized before preparation of sort keys (the
           normalization is executed after preprocess).

           A form name "Unicode::Normalize::normalize()" accepts will be applied as
           $normalization_form.  Acceptable names include 'NFD', 'NFC', 'NFKD', and 'NFKC'.  See
           "Unicode::Normalize::normalize()" for detail.  If omitted, 'NFD' is used.

           "normalization" is performed after "preprocess" (if defined).

           Furthermore, special values, "undef" and "prenormalized", can be used, though they are
           not concerned with "Unicode::Normalize::normalize()".

           If "undef" (not a string "undef") is passed explicitly as the value for this key, any
           normalization is not carried out (this may make tailoring easier if any normalization
           is not desired). Under "(normalization => undef)", only contiguous contractions are
           resolved; e.g. even if "A-ring" (and "A-ring-cedilla") is ordered after "Z",
           "A-cedilla-ring" would be primary equal to "A".  In this point, "(normalization =>
           undef, preprocess => sub { NFD(shift) })" is not equivalent to "(normalization =>
           'NFD')".

           In the case of "(normalization => "prenormalized")", any normalization is not
           performed, but discontiguous contractions with combining characters are performed.
           Therefore "(normalization => 'prenormalized', preprocess => sub { NFD(shift) })" is
           equivalent to "(normalization => 'NFD')".  If source strings are finely prenormalized,
           "(normalization => 'prenormalized')" may save time for normalization.

           Except "(normalization => undef)", Unicode::Normalize is required (see also CAVEAT).

       overrideCJK
           -- see 7.1 Derived Collation Elements, UTS #10.

           By default, CJK unified ideographs are ordered in Unicode codepoint order, but those
           in the CJK Unified Ideographs block are less than those in the CJK Unified Ideographs
           Extension A etc.

               In the CJK Unified Ideographs block:
               U+4E00..U+9FA5 if UCA_Version is 8, 9 or 11.
               U+4E00..U+9FBB if UCA_Version is 14 or 16.
               U+4E00..U+9FC3 if UCA_Version is 18.
               U+4E00..U+9FCB if UCA_Version is 20 or 22.
               U+4E00..U+9FCC if UCA_Version is 24 to 30.
               U+4E00..U+9FD5 if UCA_Version is 32 or 34.
               U+4E00..U+9FEA if UCA_Version is 36.

               In the CJK Unified Ideographs Extension blocks:
               Ext.A (U+3400..U+4DB5) and Ext.B (U+20000..U+2A6D6) in any UCA_Version.
               Ext.C (U+2A700..U+2B734) if UCA_Version is 20 or later.
               Ext.D (U+2B740..U+2B81D) if UCA_Version is 22 or later.
               Ext.E (U+2B820..U+2CEA1) if UCA_Version is 32 or later.
               Ext.F (U+2CEB0..U+2EBE0) if UCA_Version is 36.

           Through "overrideCJK", ordering of CJK unified ideographs (including extensions) can
           be overridden.

           ex. CJK unified ideographs in the JIS code point order.

             overrideCJK => sub {
                 my $u = shift;             # get a Unicode codepoint
                 my $b = pack('n', $u);     # to UTF-16BE
                 my $s = your_unicode_to_sjis_converter($b); # convert
                 my $n = unpack('n', $s);   # convert sjis to short
                 [ $n, 0x20, 0x2, $u ];     # return the collation element
             },

           The return value may be an arrayref of 1st to 4th weights as shown above. The return
           value may be an integer as the primary weight as shown below.  If "undef" is returned,
           the default derived collation element will be used.

             overrideCJK => sub {
                 my $u = shift;             # get a Unicode codepoint
                 my $b = pack('n', $u);     # to UTF-16BE
                 my $s = your_unicode_to_sjis_converter($b); # convert
                 my $n = unpack('n', $s);   # convert sjis to short
                 return $n;                 # return the primary weight
             },

           The return value may be a list containing zero or more of an arrayref, an integer, or
           "undef".

           ex. ignores all CJK unified ideographs.

             overrideCJK => sub {()}, # CODEREF returning empty list

              # where ->eq("Pe\x{4E00}rl", "Perl") is true
              # as U+4E00 is a CJK unified ideograph and to be ignorable.

           If a false value (including "undef") is passed, "overrideCJK" has no effect.
           "$Collator->change(overrideCJK => 0)" resets the old one.

           But assignment of weight for CJK unified ideographs in "table" or "entry" is still
           valid.  If "undef" is passed explicitly as the value for this key, weights for CJK
           unified ideographs are treated as undefined.  However when "UCA_Version" > 8,
           "(overrideCJK => undef)" has no special meaning.

           Note: In addition to them, 12 CJK compatibility ideographs ("U+FA0E", "U+FA0F",
           "U+FA11", "U+FA13", "U+FA14", "U+FA1F", "U+FA21", "U+FA23", "U+FA24", "U+FA27",
           "U+FA28", "U+FA29") are also treated as CJK unified ideographs. But they can't be
           overridden via "overrideCJK" when you use DUCET, as the table includes weights for
           them. "table" or "entry" has priority over "overrideCJK".

       overrideHangul
           -- see 7.1 Derived Collation Elements, UTS #10.

           By default, Hangul syllables are decomposed into Hangul Jamo, even if "(normalization
           => undef)".  But the mapping of Hangul syllables may be overridden.

           This parameter works like "overrideCJK", so see there for examples.

           If you want to override the mapping of Hangul syllables, NFD and NFKD are not
           appropriate, since NFD and NFKD will decompose Hangul syllables before overriding. FCD
           may decompose Hangul syllables as the case may be.

           If a false value (but not "undef") is passed, "overrideHangul" has no effect.
           "$Collator->change(overrideHangul => 0)" resets the old one.

           If "undef" is passed explicitly as the value for this key, weight for Hangul syllables
           is treated as undefined without decomposition into Hangul Jamo.  But definition of
           weight for Hangul syllables in "table" or "entry" is still valid.

       overrideOut
           -- see 7.1.1 Handling Ill-Formed Code Unit Sequences, UTS #10.

           Perl seems to allow out-of-range values (greater than 0x10FFFF).  By default, out-of-
           range values are replaced with "U+FFFD" (REPLACEMENT CHARACTER) when "UCA_Version" >=
           22, or ignored when "UCA_Version" <= 20.

           When "UCA_Version" >= 22, the weights of out-of-range values can be overridden. Though
           "table" or "entry" are available for them, out-of-range values are too many.

           "overrideOut" can perform it algorithmically.  This parameter works like
           "overrideCJK", so see there for examples.

           ex. ignores all out-of-range values.

             overrideOut => sub {()}, # CODEREF returning empty list

           If a false value (including "undef") is passed, "overrideOut" has no effect.
           "$Collator->change(overrideOut => 0)" resets the old one.

           NOTE ABOUT U+FFFD:

           UCA recommends that out-of-range values should not be ignored for security reasons.
           Say, "pe\x{110000}rl" should not be equal to "perl".  However, "U+FFFD" is wrongly
           mapped to a variable collation element in DUCET for Unicode 6.0.0 to 6.2.0, that means
           out-of-range values will be ignored when "variable" isn't "Non-ignorable".

           The mapping of "U+FFFD" is corrected in Unicode 6.3.0.  see
           <http://www.unicode.org/reports/tr10/tr10-28.html#Trailing_Weights> (7.1.4 Trailing
           Weights). Such a correction is reproduced by this.

             overrideOut => sub { 0xFFFD }, # CODEREF returning a very large integer

           This workaround is unnecessary since Unicode 6.3.0.

       preprocess
           -- see 5.4 Preprocessing, UTS #10.

           If specified, the coderef is used to preprocess each string before the formation of
           sort keys.

           ex. dropping English articles, such as "a" or "the".  Then, "the pen" is before "a
           pencil".

                preprocess => sub {
                      my $str = shift;
                      $str =~ s/\b(?:an?|the)\s+//gi;
                      return $str;
                   },

           "preprocess" is performed before "normalization" (if defined).

           ex. decoding strings in a legacy encoding such as shift-jis:

               $sjis_collator = Unicode::Collate->new(
                   preprocess => \&your_shiftjis_to_unicode_decoder,
               );
               @result = $sjis_collator->sort(@shiftjis_strings);

           Note: Strings returned from the coderef will be interpreted according to Perl's
           Unicode support. See perlunicode, perluniintro, perlunitut, perlunifaq, utf8.

       rearrange
           -- see 3.5 Rearrangement, UTS #10.

           Characters that are not coded in logical order and to be rearranged.  If "UCA_Version"
           is equal to or less than 11, default is:

               rearrange => [ 0x0E40..0x0E44, 0x0EC0..0x0EC4 ],

           If you want to disallow any rearrangement, pass "undef" or "[]" (a reference to empty
           list) as the value for this key.

           If "UCA_Version" is equal to or greater than 14, default is "[]" (i.e. no
           rearrangement).

           According to the version 9 of UCA, this parameter shall not be used; but it is not
           warned at present.

       rewrite
           If specified, the coderef is used to rewrite lines in "table" or "entry".  The coderef
           will get each line, and then should return a rewritten line according to the UCA file
           format.  If the coderef returns an empty line, the line will be skipped.

           e.g. any primary ignorable characters into tertiary ignorable:

               rewrite => sub {
                   my $line = shift;
                   $line =~ s/\[\.0000\..{4}\..{4}\./[.0000.0000.0000./g;
                   return $line;
               },

           This example shows rewriting weights. "rewrite" is allowed to affect code points,
           weights, and the name.

           NOTE: "table" is available to use another table file; preparing a modified table once
           would be more efficient than rewriting lines on reading an unmodified table every
           time.

       suppress
           -- see 3.12 Special-Purpose Commands, UTS #35 (LDML) Part 5: Collation.

           Contractions beginning with the specified characters are suppressed, even if those
           contractions are defined in "table".

           An example for Russian and some languages using the Cyrillic script:

               suppress => [0x0400..0x0417, 0x041A..0x0437, 0x043A..0x045F],

           where 0x0400 stands for "U+0400", CYRILLIC CAPITAL LETTER IE WITH GRAVE.

           NOTE: Contractions via "entry" will not be suppressed.

       table
           -- see 3.8 Default Unicode Collation Element Table, UTS #10.

           You can use another collation element table if desired.

           The table file should locate in the Unicode/Collate directory on @INC. Say, if the
           filename is Foo.txt, the table file is searched as Unicode/Collate/Foo.txt in @INC.

           By default, allkeys.txt (as the filename of DUCET) is used.  If you will prepare your
           own table file, any name other than allkeys.txt may be better to avoid namespace
           conflict.

           NOTE: When XSUB is used, the DUCET is compiled on building this module, and it may
           save time at the run time.  Explicit saying "(table => 'allkeys.txt')", or using
           another table, or using "ignoreChar", "ignoreName", "undefChar", "undefName" or
           "rewrite" will prevent this module from using the compiled DUCET.

           If "undef" is passed explicitly as the value for this key, no file is read (but you
           can define collation elements via "entry").

           A typical way to define a collation element table without any file of table:

              $onlyABC = Unicode::Collate->new(
                  table => undef,
                  entry => << 'ENTRIES',
           0061 ; [.0101.0020.0002.0061] # LATIN SMALL LETTER A
           0041 ; [.0101.0020.0008.0041] # LATIN CAPITAL LETTER A
           0062 ; [.0102.0020.0002.0062] # LATIN SMALL LETTER B
           0042 ; [.0102.0020.0008.0042] # LATIN CAPITAL LETTER B
           0063 ; [.0103.0020.0002.0063] # LATIN SMALL LETTER C
           0043 ; [.0103.0020.0008.0043] # LATIN CAPITAL LETTER C
           ENTRIES
               );

           If "ignoreName" or "undefName" is used, character names should be specified as a
           comment (following "#") on each line.

       undefChar
       undefName
           -- see 6.3.3 Reducing the Repertoire, UTS #10.

           Undefines the collation element as if it were unassigned in the "table".  This reduces
           the size of the table.  If an unassigned character appears in the string to be
           collated, the sort key is made from its codepoint as a single-character collation
           element, as it is greater than any other assigned collation elements (in the codepoint
           order among the unassigned characters).  But, it'd be better to ignore characters
           unfamiliar to you and maybe never used.

           Through "undefChar", any character matching "qr/$undefChar/" will be undefined.
           Through "undefName", any character whose name (given in the "table" file as a comment)
           matches "qr/$undefName/" will be undefined.

           ex. Collation weights for beyond-BMP characters are not stored in object:

               undefChar => qr/[^\0-\x{fffd}]/,

       upper_before_lower
           -- see 6.6 Case Comparisons, UTS #10.

           By default, lowercase is before uppercase.  If the parameter is made true, this is
           reversed.

           NOTE: This parameter simplemindedly assumes that any lowercase/uppercase distinctions
           must occur in level 3, and their weights at level 3 must be same as those mentioned in
           7.3.1, UTS #10.  If you define your collation elements which differs from this
           requirement, this parameter doesn't work validly.

       variable
           -- see 3.6 Variable Weighting, UTS #10.

           This key allows for variable weighting of variable collation elements, which are
           marked with an ASTERISK in the table (NOTE: Many punctuation marks and symbols are
           variable in allkeys.txt).

              variable => 'blanked', 'non-ignorable', 'shifted', or 'shift-trimmed'.

           These names are case-insensitive.  By default (if specification is omitted), 'shifted'
           is adopted.

              'Blanked'        Variable elements are made ignorable at levels 1 through 3;
                               considered at the 4th level.

              'Non-Ignorable'  Variable elements are not reset to ignorable.

              'Shifted'        Variable elements are made ignorable at levels 1 through 3
                               their level 4 weight is replaced by the old level 1 weight.
                               Level 4 weight for Non-Variable elements is 0xFFFF.

              'Shift-Trimmed'  Same as 'shifted', but all FFFF's at the 4th level
                               are trimmed.

   Methods for Collation
       "@sorted = $Collator->sort(@not_sorted)"
           Sorts a list of strings.

       "$result = $Collator->cmp($a, $b)"
           Returns 1 (when $a is greater than $b) or 0 (when $a is equal to $b) or -1 (when $a is
           less than $b).

       "$result = $Collator->eq($a, $b)"
       "$result = $Collator->ne($a, $b)"
       "$result = $Collator->lt($a, $b)"
       "$result = $Collator->le($a, $b)"
       "$result = $Collator->gt($a, $b)"
       "$result = $Collator->ge($a, $b)"
           They works like the same name operators as theirs.

              eq : whether $a is equal to $b.
              ne : whether $a is not equal to $b.
              lt : whether $a is less than $b.
              le : whether $a is less than $b or equal to $b.
              gt : whether $a is greater than $b.
              ge : whether $a is greater than $b or equal to $b.

       "$sortKey = $Collator->getSortKey($string)"
           -- see 4.3 Form Sort Key, UTS #10.

           Returns a sort key.

           You compare the sort keys using a binary comparison and get the result of the
           comparison of the strings using UCA.

              $Collator->getSortKey($a) cmp $Collator->getSortKey($b)

                 is equivalent to

              $Collator->cmp($a, $b)

       "$sortKeyForm = $Collator->viewSortKey($string)"
           Converts a sorting key into its representation form.  If "UCA_Version" is 8, the
           output is slightly different.

              use Unicode::Collate;
              my $c = Unicode::Collate->new();
              print $c->viewSortKey("Perl"),"\n";

              # output:
              # [0B67 0A65 0B7F 0B03 | 0020 0020 0020 0020 | 0008 0002 0002 0002 | FFFF FFFF FFFF FFFF]
              #  Level 1               Level 2               Level 3               Level 4

   Methods for Searching
       The "match", "gmatch", "subst", "gsubst" methods work like "m//", "m//g", "s///", "s///g",
       respectively, but they are not aware of any pattern, but only a literal substring.

       DISCLAIMER: If "preprocess" or "normalization" parameter is true for $Collator, calling
       these methods ("index", "match", "gmatch", "subst", "gsubst") is croaked, as the position
       and the length might differ from those on the specified string.

       "rearrange" and "hangul_terminator" parameters are neglected.  "katakana_before_hiragana"
       and "upper_before_lower" don't affect matching and searching, as it doesn't matter whether
       greater or less.

       "$position = $Collator->index($string, $substring[, $position])"
       "($position, $length) = $Collator->index($string, $substring[, $position])"
           If $substring matches a part of $string, returns the position of the first occurrence
           of the matching part in scalar context; in list context, returns a two-element list of
           the position and the length of the matching part.

           If $substring does not match any part of $string, returns "-1" in scalar context and
           an empty list in list context.

           e.g. when the content of $str is ""Ich mu"ß" studieren Perl."", you say the following
           where $sub is ""M"ü"SS"",

             my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
                                                # (normalization => undef) is REQUIRED.
             my $match;
             if (my($pos,$len) = $Collator->index($str, $sub)) {
                 $match = substr($str, $pos, $len);
             }

           and get ""mu"ß""" in $match, since ""mu"ß""" is primary equal to ""M"ü"SS"".

       "$match_ref = $Collator->match($string, $substring)"
       "($match)   = $Collator->match($string, $substring)"
           If $substring matches a part of $string, in scalar context, returns a reference to the
           first occurrence of the matching part ($match_ref is always true if matches, since
           every reference is true); in list context, returns the first occurrence of the
           matching part.

           If $substring does not match any part of $string, returns "undef" in scalar context
           and an empty list in list context.

           e.g.

               if ($match_ref = $Collator->match($str, $sub)) { # scalar context
                   print "matches [$$match_ref].\n";
               } else {
                   print "doesn't match.\n";
               }

                or

               if (($match) = $Collator->match($str, $sub)) { # list context
                   print "matches [$match].\n";
               } else {
                   print "doesn't match.\n";
               }

       "@match = $Collator->gmatch($string, $substring)"
           If $substring matches a part of $string, returns all the matching parts (or matching
           count in scalar context).

           If $substring does not match any part of $string, returns an empty list.

       "$count = $Collator->subst($string, $substring, $replacement)"
           If $substring matches a part of $string, the first occurrence of the matching part is
           replaced by $replacement ($string is modified) and $count (always equals to 1) is
           returned.

           $replacement can be a "CODEREF", taking the matching part as an argument, and
           returning a string to replace the matching part (a bit similar to
           "s/(..)/$coderef->($1)/e").

       "$count = $Collator->gsubst($string, $substring, $replacement)"
           If $substring matches a part of $string, all the occurrences of the matching part are
           replaced by $replacement ($string is modified) and $count is returned.

           $replacement can be a "CODEREF", taking the matching part as an argument, and
           returning a string to replace the matching part (a bit similar to
           "s/(..)/$coderef->($1)/eg").

           e.g.

             my $Collator = Unicode::Collate->new( normalization => undef, level => 1 );
                                                # (normalization => undef) is REQUIRED.
             my $str = "Camel donkey zebra came\x{301}l CAMEL horse cam\0e\0l...";
             $Collator->gsubst($str, "camel", sub { "<b>$_[0]</b>" });

             # now $str is "<b>Camel</b> donkey zebra <b>came\x{301}l</b> <b>CAMEL</b> horse <b>cam\0e\0l</b>...";
             # i.e., all the camels are made bold-faced.

              Examples: levels and ignore_level2 - what does camel match?
             ---------------------------------------------------------------------------
              level  ignore_level2  |  camel  Camel  came\x{301}l  c-a-m-e-l  cam\0e\0l
             -----------------------|---------------------------------------------------
                1        false      |   yes    yes      yes          yes        yes
                2        false      |   yes    yes      no           yes        yes
                3        false      |   yes    no       no           yes        yes
                4        false      |   yes    no       no           no         yes
             -----------------------|---------------------------------------------------
                1        true       |   yes    yes      yes          yes        yes
                2        true       |   yes    yes      yes          yes        yes
                3        true       |   yes    no       yes          yes        yes
                4        true       |   yes    no       yes          no         yes
             ---------------------------------------------------------------------------
              note: if variable => non-ignorable, camel doesn't match c-a-m-e-l
                    at any level.

   Other Methods
       "%old_tailoring = $Collator->change(%new_tailoring)"
       "$modified_collator = $Collator->change(%new_tailoring)"
           Changes the value of specified keys and returns the changed part.

               $Collator = Unicode::Collate->new(level => 4);

               $Collator->eq("perl", "PERL"); # false

               %old = $Collator->change(level => 2); # returns (level => 4).

               $Collator->eq("perl", "PERL"); # true

               $Collator->change(%old); # returns (level => 2).

               $Collator->eq("perl", "PERL"); # false

           Not all "(key,value)"s are allowed to be changed.  See also
           @Unicode::Collate::ChangeOK and @Unicode::Collate::ChangeNG.

           In the scalar context, returns the modified collator (but it is not a clone from the
           original).

               $Collator->change(level => 2)->eq("perl", "PERL"); # true

               $Collator->eq("perl", "PERL"); # true; now max level is 2nd.

               $Collator->change(level => 4)->eq("perl", "PERL"); # false

       "$version = $Collator->version()"
           Returns the version number (a string) of the Unicode Standard which the "table" file
           used by the collator object is based on.  If the table does not include a version line
           (starting with @version), returns "unknown".

       "UCA_Version()"
           Returns the revision number of UTS #10 this module consults, that should correspond
           with the DUCET incorporated.

       "Base_Unicode_Version()"
           Returns the version number of UTS #10 this module consults, that should correspond
           with the DUCET incorporated.

EXPORT

       No method will be exported.

INSTALL

       Though this module can be used without any "table" file, to use this module easily, it is
       recommended to install a table file in the UCA format, by copying it under the directory
       <a place in @INC>/Unicode/Collate.

       The most preferable one is "The Default Unicode Collation Element Table" (aka DUCET),
       available from the Unicode Consortium's website:

          http://www.unicode.org/Public/UCA/

          http://www.unicode.org/Public/UCA/latest/allkeys.txt
          (latest version)

       If DUCET is not installed, it is recommended to copy the file from
       http://www.unicode.org/Public/UCA/latest/allkeys.txt to <a place in
       @INC>/Unicode/Collate/allkeys.txt manually.

CAVEATS

       Normalization
           Use of the "normalization" parameter requires the Unicode::Normalize module (see
           Unicode::Normalize).

           If you need not it (say, in the case when you need not handle any combining
           characters), assign "(normalization => undef)" explicitly.

           -- see 6.5 Avoiding Normalization, UTS #10.

       Conformance Test
           The Conformance Test for the UCA is available under
           <http://www.unicode.org/Public/UCA/>.

           For CollationTest_SHIFTED.txt, a collator via "Unicode::Collate->new( )" should be
           used; for CollationTest_NON_IGNORABLE.txt, a collator via
           "Unicode::Collate->new(variable => "non-ignorable", level => 3)".

           If "UCA_Version" is 26 or later, the "identical" level is preferred;
           "Unicode::Collate->new(identical => 1)" and "Unicode::Collate->new(identical => 1,"
           "variable => "non-ignorable", level => 3)" should be used.

           Unicode::Normalize is required to try The Conformance Test.

AUTHOR, COPYRIGHT AND LICENSE

       The Unicode::Collate module for perl was written by SADAHIRO Tomoyuki,
       <SADAHIRO@cpan.org>. This module is Copyright(C) 2001-2018, SADAHIRO Tomoyuki. Japan. All
       rights reserved.

       This module is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.

       The file Unicode/Collate/allkeys.txt was copied verbatim from
       <http://www.unicode.org/Public/UCA/9.0.0/allkeys.txt>.  For this file, Copyright (c) 2016
       Unicode, Inc.; distributed under the Terms of Use in
       <http://www.unicode.org/terms_of_use.html>

SEE ALSO

       Unicode Collation Algorithm - UTS #10
           <http://www.unicode.org/reports/tr10/>

       The Default Unicode Collation Element Table (DUCET)
           <http://www.unicode.org/Public/UCA/latest/allkeys.txt>

       The conformance test for the UCA
           <http://www.unicode.org/Public/UCA/latest/CollationTest.html>

           <http://www.unicode.org/Public/UCA/latest/CollationTest.zip>

       Hangul Syllable Type
           <http://www.unicode.org/Public/UNIDATA/HangulSyllableType.txt>

       Unicode Normalization Forms - UAX #15
           <http://www.unicode.org/reports/tr15/>

       Unicode Locale Data Markup Language (LDML) - UTS #35
           <http://www.unicode.org/reports/tr35/>