Provided by: perl-doc_5.26.1-6ubuntu0.7_all 
NAME
version - Perl extension for Version Objects
SYNOPSIS
# Parsing version strings (decimal or dotted-decimal)
use version 0.77; # get latest bug-fixes and API
$ver = version->parse($string)
# Declaring a dotted-decimal $VERSION (keep on one line!)
use version; our $VERSION = version->declare("v1.2.3"); # formal
use version; our $VERSION = qv("v1.2.3"); # deprecated
use version; our $VERSION = qv("v1.2_3"); # deprecated
# Declaring an old-style decimal $VERSION (use quotes!)
our $VERSION = "1.0203"; # recommended
use version; our $VERSION = version->parse("1.0203"); # formal
use version; our $VERSION = version->parse("1.02_03"); # alpha
# Comparing mixed version styles (decimals, dotted-decimals, objects)
if ( version->parse($v1) == version->parse($v2) ) {
# do stuff
}
# Sorting mixed version styles
@ordered = sort { version->parse($a) <=> version->parse($b) } @list;
DESCRIPTION
Version objects were added to Perl in 5.10. This module implements version objects for
older version of Perl and provides the version object API for all versions of Perl. All
previous releases before 0.74 are deprecated and should not be used due to incompatible
API changes. Version 0.77 introduces the new 'parse' and 'declare' methods to standardize
usage. You are strongly urged to set 0.77 as a minimum in your code, e.g.
use version 0.77; # even for Perl v.5.10.0
TYPES OF VERSION OBJECTS
There are two different types of version objects, corresponding to the two different
styles of versions in use:
Decimal Versions
The classic floating-point number $VERSION. The advantage to this style is that you
don't need to do anything special, just type a number into your source file. Quoting is
recommended, as it ensures that trailing zeroes ("1.50") are preserved in any warnings
or other output.
Dotted Decimal Versions
The more modern form of version assignment, with 3 (or potentially more) integers
separated by decimal points (e.g. v1.2.3). This is the form that Perl itself has used
since 5.6.0 was released. The leading 'v' is now strongly recommended for clarity, and
will throw a warning in a future release if omitted. A leading 'v' character is
required to pass the "is_strict()" test.
DECLARING VERSIONS
If you have a module that uses a decimal $VERSION (floating point), and you do not intend
to ever change that, this module is not for you. There is nothing that version.pm gains
you over a simple $VERSION assignment:
our $VERSION = "1.02";
Since Perl v5.10.0 includes the version.pm comparison logic anyways, you don't need to do
anything at all.
How to convert a module from decimal to dotted-decimal
If you have used a decimal $VERSION in the past and wish to switch to a dotted-decimal
$VERSION, then you need to make a one-time conversion to the new format.
Important Note: you must ensure that your new $VERSION is numerically greater than your
current decimal $VERSION; this is not always obvious. First, convert your old decimal
version (e.g. 1.02) to a normalized dotted-decimal form:
$ perl -Mversion -e 'print version->parse("1.02")->normal'
v1.20.0
Then increment any of the dotted-decimal components (v1.20.1 or v1.21.0).
How to "declare()" a dotted-decimal version
use version; our $VERSION = version->declare("v1.2.3");
The "declare()" method always creates dotted-decimal version objects. When used in a
module, you must put it on the same line as "use version" to ensure that $VERSION is read
correctly by PAUSE and installer tools. You should also add 'version' to the
'configure_requires' section of your module metadata file. See instructions in
ExtUtils::MakeMaker or Module::Build for details.
Important Note: Even if you pass in what looks like a decimal number ("1.2"), a dotted-
decimal will be created ("v1.200.0"). To avoid confusion or unintentional errors on older
Perls, follow these guidelines:
• Always use a dotted-decimal with (at least) three components
• Always use a leading-v
• Always quote the version
If you really insist on using version.pm with an ordinary decimal version, use "parse()"
instead of declare. See the "PARSING AND COMPARING VERSIONS" for details.
See also version::Internals for more on version number conversion, quoting, calculated
version numbers and declaring developer or "alpha" version numbers.
PARSING AND COMPARING VERSIONS
If you need to compare version numbers, but can't be sure whether they are expressed as
numbers, strings, v-strings or version objects, then you should use version.pm to parse
them all into objects for comparison.
How to "parse()" a version
The "parse()" method takes in anything that might be a version and returns a corresponding
version object, doing any necessary conversion along the way.
• Dotted-decimal: bare v-strings (v1.2.3) and strings with more than one decimal point and
a leading 'v' ("v1.2.3"); NOTE you can technically use a v-string or strings with a
leading-v and only one decimal point (v1.2 or "v1.2"), but you will confuse both
yourself and others.
• Decimal: regular decimal numbers (literal or in a string)
Some examples:
$variable version->parse($variable)
--------- -------------------------
1.23 v1.230.0
"1.23" v1.230.0
v1.23 v1.23.0
"v1.23" v1.23.0
"1.2.3" v1.2.3
"v1.2.3" v1.2.3
See version::Internals for more on version number conversion.
How to check for a legal version string
If you do not want to actually create a full blown version object, but would still like to
verify that a given string meets the criteria to be parsed as a version, there are two
helper functions that can be employed directly:
"is_lax()"
The lax criteria corresponds to what is currently allowed by the version parser. All
of the following formats are acceptable for dotted-decimal formats strings:
v1.2
1.2345.6
v1.23_4
1.2345
1.2345_01
"is_strict()"
If you want to limit yourself to a much more narrow definition of what a version
string constitutes, "is_strict()" is limited to version strings like the following
list:
v1.234.5
2.3456
See version::Internals for details of the regular expressions that define the legal
version string forms, as well as how to use those regular expressions in your own code if
"is_lax()" and "is_strict()" are not sufficient for your needs.
How to compare version objects
Version objects overload the "cmp" and "<=>" operators. Perl automatically generates all
of the other comparison operators based on those two so all the normal logical comparisons
will work.
if ( version->parse($v1) == version->parse($v2) ) {
# do stuff
}
If a version object is compared against a non-version object, the non-object term will be
converted to a version object using "parse()". This may give surprising results:
$v1 = version->parse("v0.95.0");
$bool = $v1 < 0.96; # FALSE since 0.96 is v0.960.0
Always comparing to a version object will help avoid surprises:
$bool = $v1 < version->parse("v0.96.0"); # TRUE
Note that "alpha" version objects (where the version string contains a trailing underscore
segment) compare as less than the equivalent version without an underscore:
$bool = version->parse("1.23_45") < version->parse("1.2345"); # TRUE
See version::Internals for more details on "alpha" versions.
OBJECT METHODS
is_alpha()
True if and only if the version object was created with a underscore, e.g.
version->parse('1.002_03')->is_alpha; # TRUE
version->declare('1.2.3_4')->is_alpha; # TRUE
is_qv()
True only if the version object is a dotted-decimal version, e.g.
version->parse('v1.2.0')->is_qv; # TRUE
version->declare('v1.2')->is_qv; # TRUE
qv('1.2')->is_qv; # TRUE
version->parse('1.2')->is_qv; # FALSE
normal()
Returns a string with a standard 'normalized' dotted-decimal form with a leading-v and at
least 3 components.
version->declare('v1.2')->normal; # v1.2.0
version->parse('1.2')->normal; # v1.200.0
numify()
Returns a value representing the object in a pure decimal form without trailing zeroes.
version->declare('v1.2')->numify; # 1.002
version->parse('1.2')->numify; # 1.200
stringify()
Returns a string that is as close to the original representation as possible. If the
original representation was a numeric literal, it will be returned the way perl would
normally represent it in a string. This method is used whenever a version object is
interpolated into a string.
version->declare('v1.2')->stringify; # v1.2
version->parse('1.200')->stringify; # 1.200
version->parse(1.02_30)->stringify; # 1.023
EXPORTED FUNCTIONS
qv()
This function is no longer recommended for use, but is maintained for compatibility with
existing code. If you do not want to have it exported to your namespace, use this form:
use version 0.77 ();
is_lax()
(Not exported by default)
This function takes a scalar argument and returns a boolean value indicating whether the
argument meets the "lax" rules for a version number. Leading and trailing spaces are not
allowed.
is_strict()
(Not exported by default)
This function takes a scalar argument and returns a boolean value indicating whether the
argument meets the "strict" rules for a version number. Leading and trailing spaces are
not allowed.
AUTHOR
John Peacock <jpeacock@cpan.org>
SEE ALSO
version::Internals.
perl.