NAME

       Data::Munge - various utility functions

SYNOPSIS

        use Data::Munge;

        my $re = list2re qw/foo bar baz/;

        print byval { s/foo/bar/ } $text;
        foo(mapval { chomp } @lines);

        print replace('Apples are round, and apples are juicy.', qr/apples/i, 'oranges', 'g');
        print replace('John Smith', qr/(\w+)\s+(\w+)/, '$2, $1');

        my $trimmed = trim "  a b c "; # "a b c"

        my $x = 'bar';
        if (elem $x, [qw(foo bar baz)]) { ... }

        eval_string('print "hello world\\n"');  # says hello
        eval_string('die');  # dies
        eval_string('{');    # throws a syntax error

        my $fac = rec {
          my ($rec, $n) = @_;
          $n < 2 ? 1 : $n * $rec->($n - 1)
        };
        print $fac->(5);  # 120

DESCRIPTION

       This module defines a few generally useful utility functions. I got tired of redefining or
       working around them, so I wrote this module.

   Functions
       list2re LIST
           Converts a list of strings to a regex that matches any of the strings.  Especially
           useful in combination with "keys". Example:

            my $re = list2re keys %hash;
            $str =~ s/($re)/$hash{$1}/g;

       byval BLOCK SCALAR
           Takes a code block and a value, runs the block with $_ set to that value, and returns
           the final value of $_. The global value of $_ is not affected. $_ isn't aliased to the
           input value either, so modifying $_ in the block will not affect the passed in value.
           Example:

            foo(byval { s/!/?/g } $str);
            # Calls foo() with the value of $str, but all '!' have been replaced by '?'.
            # $str itself is not modified.

       mapval BLOCK LIST
           Works like a combination of "map" and "byval"; i.e. it behaves like "map", but $_ is a
           copy, not aliased to the current element, and the return value is taken from $_ again
           (it ignores the value returned by the block). Example:

            my @foo = mapval { chomp } @bar;
            # @foo contains a copy of @bar where all elements have been chomp'd.
            # This could also be written as chomp(my @foo = @bar); but that's not
            # always possible.

       submatches
           Returns a list of the strings captured by the last successful pattern match.  Normally
           you don't need this function because this is exactly what "m//" returns in list
           context. However, "submatches" also works in other contexts such as the RHS of
           "s//.../e".

       replace STRING, REGEX, REPLACEMENT, FLAG
       replace STRING, REGEX, REPLACEMENT
           A clone of javascript's "String.prototype.replace". It works almost the same as "byval
           { s/REGEX/REPLACEMENT/FLAG } STRING", but with a few important differences. REGEX can
           be a string or a compiled "qr//" object. REPLACEMENT can be a string or a subroutine
           reference. If it's a string, it can contain the following replacement patterns:

           $$  Inserts a '$'.

           $&  Inserts the matched substring.

           $`  Inserts the substring preceding the match.

           $'  Inserts the substring following the match.

           $N  (where N is a digit)
               Inserts the substring matched by the Nth capturing group.

           ${N}  (where N is one or more digits)
               Inserts the substring matched by the Nth capturing group.

           Note that these aren't variables; they're character sequences interpreted by
           "replace".

           If REPLACEMENT is a subroutine reference, it's called with the following arguments:
           First the matched substring (like $& above), then the contents of the capture buffers
           (as returned by "submatches"), then the offset where the pattern matched (like
           "$-[0]", see "@-" in perlvar), then the STRING. The return value will be inserted in
           place of the matched substring.

           Normally only the first occurrence of REGEX is replaced. If FLAG is present, it must
           be 'g' and causes all occurrences to be replaced.

       trim STRING
           Returns STRING with all leading and trailing whitespace removed.

       elem SCALAR, ARRAYREF
           Returns a boolean value telling you whether SCALAR is an element of ARRAYREF or not.
           Two scalars are considered equal if they're both "undef", if they're both references
           to the same thing, or if they're both not references and "eq" to each other.

           This is implemented as a linear search through ARRAYREF that terminates early if a
           match is found (i.e. "elem 'A', ['A', 1 .. 9999]" won't even look at elements "1 ..
           9999").

       eval_string STRING
           Evals STRING just like "eval" but doesn't catch exceptions.

       rec BLOCK
           Creates an anonymous sub as "sub BLOCK" would, but supplies the called sub with an
           extra argument that can be used to recurse:

            my $code = rec {
              my ($rec, $n) = @_;
              $rec->($n - 1) if $n > 0;
              print $n, "\n";
            };
            $code->(4);

           That is, when the sub is called, an implicit first argument is passed in $_[0] (all
           normal arguments are moved one up). This first argument is a reference to the sub
           itself. This reference could be used to recurse directly or to register the sub as a
           handler in an event system, for example.

           A note on defining recursive anonymous functions: Doing this right is more complicated
           than it may at first appear. The most straightforward solution using a lexical
           variable and a closure leaks memory because it creates a reference cycle. Starting
           with perl 5.16 there is a "__SUB__" constant that is equivalent to $rec above, and
           this is indeed what this module uses (if available).

           However, this module works even on older perls by falling back to either weak
           references (if available) or a "fake recursion" scheme that dynamically instantiates a
           new sub for each call instead of creating a cycle. This last resort is slower than
           weak references but works everywhere.

AUTHOR

       Lukas Mai, "<l.mai at web.de>"

COPYRIGHT & LICENSE

       Copyright 2009-2011, 2013 Lukas Mai.

       This program is free software; you can redistribute it and/or modify it under the terms of
       either: the GNU General Public License as published by the Free Software Foundation; or
       the Artistic License.

       See http://dev.perl.org/licenses/ for more information.