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authorNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
committerNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
commite0c6872cf40896c7be36b11dcc744620f10adf1d (patch)
tree60335e10d2f4354b0674ec22d7b53f0f8abee672 /systems/texlive/tlnet/tlpkg/tlperl/lib/version
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+=head1 NAME
+
+version::Internals - Perl extension for Version Objects
+
+=head1 DESCRIPTION
+
+Overloaded version objects for all modern versions of Perl. This documents
+the internal data representation and underlying code for version.pm. See
+F<version.pod> for daily usage. This document is only useful for users
+interested in the gory details.
+
+=head1 WHAT IS A VERSION?
+
+For the purposes of this module, a version "number" is a sequence of
+positive integer values separated by one or more decimal points and
+optionally a single underscore. This corresponds to what Perl itself
+uses for a version, as well as extending the "version as number" that
+is discussed in the various editions of the Camel book.
+
+There are actually two distinct kinds of version objects:
+
+=over 4
+
+=item Decimal versions
+
+Any version which "looks like a number", see L<Decimal Versions>. This
+also includes versions with a single decimal point and a single embedded
+underscore, see L<Alpha Versions>, even though these must be quoted
+to preserve the underscore formatting.
+
+=item Dotted-Decimal versions
+
+Also referred to as "Dotted-Integer", these contains more than one decimal
+point and may have an optional embedded underscore, see L<Dotted-Decimal
+Versions>. This is what is commonly used in most open source software as
+the "external" version (the one used as part of the tag or tarfile name).
+A leading 'v' character is now required and will warn if it missing.
+
+=back
+
+Both of these methods will produce similar version objects, in that
+the default stringification will yield the version L<Normal Form> only
+if required:
+
+ $v = version->new(1.002); # 1.002, but compares like 1.2.0
+ $v = version->new(1.002003); # 1.002003
+ $v2 = version->new("v1.2.3"); # v1.2.3
+
+In specific, version numbers initialized as L<Decimal Versions> will
+stringify as they were originally created (i.e. the same string that was
+passed to C<new()>. Version numbers initialized as L<Dotted-Decimal Versions>
+will be stringified as L<Normal Form>.
+
+=head2 Decimal Versions
+
+These correspond to historical versions of Perl itself prior to 5.6.0,
+as well as all other modules which follow the Camel rules for the
+$VERSION scalar. A Decimal version is initialized with what looks like
+a floating point number. Leading zeros B<are> significant and trailing
+zeros are implied so that a minimum of three places is maintained
+between subversions. What this means is that any subversion (digits
+to the right of the decimal place) that contains less than three digits
+will have trailing zeros added to make up the difference, but only for
+purposes of comparison with other version objects. For example:
+
+ # Prints Equivalent to
+ $v = version->new( 1.2); # 1.2 v1.200.0
+ $v = version->new( 1.02); # 1.02 v1.20.0
+ $v = version->new( 1.002); # 1.002 v1.2.0
+ $v = version->new( 1.0023); # 1.0023 v1.2.300
+ $v = version->new( 1.00203); # 1.00203 v1.2.30
+ $v = version->new( 1.002003); # 1.002003 v1.2.3
+
+All of the preceding examples are true whether or not the input value is
+quoted. The important feature is that the input value contains only a
+single decimal. See also L<Alpha Versions>.
+
+IMPORTANT NOTE: As shown above, if your Decimal version contains more
+than 3 significant digits after the decimal place, it will be split on
+each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need
+to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation.
+Any trailing zeros are ignored for mathematical comparison purposes.
+
+=head2 Dotted-Decimal Versions
+
+These are the newest form of versions, and correspond to Perl's own
+version style beginning with 5.6.0. Starting with Perl 5.10.0,
+and most likely Perl 6, this is likely to be the preferred form. This
+method normally requires that the input parameter be quoted, although
+Perl's after 5.8.1 can use v-strings as a special form of quoting, but
+this is highly discouraged.
+
+Unlike L<Decimal Versions>, Dotted-Decimal Versions have more than
+a single decimal point, e.g.:
+
+ # Prints
+ $v = version->new( "v1.200"); # v1.200.0
+ $v = version->new("v1.20.0"); # v1.20.0
+ $v = qv("v1.2.3"); # v1.2.3
+ $v = qv("1.2.3"); # v1.2.3
+ $v = qv("1.20"); # v1.20.0
+
+In general, Dotted-Decimal Versions permit the greatest amount of freedom
+to specify a version, whereas Decimal Versions enforce a certain
+uniformity.
+
+Just like L</Decimal Versions>, Dotted-Decimal Versions can be used as
+L</Alpha Versions>.
+
+=head2 Alpha Versions
+
+For module authors using CPAN, the convention has been to note unstable
+releases with an underscore in the version string. (See L<CPAN>.) version.pm
+follows this convention and alpha releases will test as being newer than the
+more recent stable release, and less than the next stable release. Only the
+last element may be separated by an underscore:
+
+ # Declaring
+ use version 0.77; our $VERSION = version->declare("v1.2_3");
+
+ # Parsing
+ $v1 = version->parse("v1.2_3");
+ $v1 = version->parse("1.002_003");
+
+Note that you B<must> quote the version when writing an alpha Decimal version.
+The stringified form of Decimal versions will always be the same string that
+was used to initialize the version object.
+
+=head2 Regular Expressions for Version Parsing
+
+A formalized definition of the legal forms for version strings is
+included in the C<version::regex> class. Primitives are included for
+common elements, although they are scoped to the file so they are useful
+for reference purposes only. There are two publicly accessible scalars
+that can be used in other code (not exported):
+
+=over 4
+
+=item C<$version::LAX>
+
+This regexp covers all of the legal forms allowed under the current
+version string parser. This is not to say that all of these forms
+are recommended, and some of them can only be used when quoted.
+
+For dotted decimals:
+
+ v1.2
+ 1.2345.6
+ v1.23_4
+
+The leading 'v' is optional if two or more decimals appear. If only
+a single decimal is included, then the leading 'v' is required to
+trigger the dotted-decimal parsing. A leading zero is permitted,
+though not recommended except when quoted, because of the risk that
+Perl will treat the number as octal. A trailing underscore plus one
+or more digits denotes an alpha or development release (and must be
+quoted to be parsed properly).
+
+For decimal versions:
+
+ 1
+ 1.2345
+ 1.2345_01
+
+an integer portion, an optional decimal point, and optionally one or
+more digits to the right of the decimal are all required. A trailing
+underscore is permitted and a leading zero is permitted. Just like
+the lax dotted-decimal version, quoting the values is required for
+alpha/development forms to be parsed correctly.
+
+=item C<$version::STRICT>
+
+This regexp covers a much more limited set of formats and constitutes
+the best practices for initializing version objects. Whether you choose
+to employ decimal or dotted-decimal for is a personal preference however.
+
+=over 4
+
+=item v1.234.5
+
+For dotted-decimal versions, a leading 'v' is required, with three or
+more sub-versions of no more than three digits. A leading 0 (zero)
+before the first sub-version (in the above example, '1') is also
+prohibited.
+
+=item 2.3456
+
+For decimal versions, an integer portion (no leading 0), a decimal point,
+and one or more digits to the right of the decimal are all required.
+
+=back
+
+=back
+
+Both of the provided scalars are already compiled as regular expressions
+and do not contain either anchors or implicit groupings, so they can be
+included in your own regular expressions freely. For example, consider
+the following code:
+
+ ($pkg, $ver) =~ /
+ ^[ \t]*
+ use [ \t]+($PKGNAME)
+ (?:[ \t]+($version::STRICT))?
+ [ \t]*;
+ /x;
+
+This would match a line of the form:
+
+ use Foo::Bar::Baz v1.2.3; # legal only in Perl 5.8.1+
+
+where C<$PKGNAME> is another regular expression that defines the legal
+forms for package names.
+
+=head1 IMPLEMENTATION DETAILS
+
+=head2 Equivalence between Decimal and Dotted-Decimal Versions
+
+When Perl 5.6.0 was released, the decision was made to provide a
+transformation between the old-style decimal versions and new-style
+dotted-decimal versions:
+
+ 5.6.0 == 5.006000
+ 5.005_04 == 5.5.40
+
+The floating point number is taken and split first on the single decimal
+place, then each group of three digits to the right of the decimal makes up
+the next digit, and so on until the number of significant digits is exhausted,
+B<plus> enough trailing zeros to reach the next multiple of three.
+
+This was the method that version.pm adopted as well. Some examples may be
+helpful:
+
+ equivalent
+ decimal zero-padded dotted-decimal
+ ------- ----------- --------------
+ 1.2 1.200 v1.200.0
+ 1.02 1.020 v1.20.0
+ 1.002 1.002 v1.2.0
+ 1.0023 1.002300 v1.2.300
+ 1.00203 1.002030 v1.2.30
+ 1.002003 1.002003 v1.2.3
+
+=head2 Quoting Rules
+
+Because of the nature of the Perl parsing and tokenizing routines,
+certain initialization values B<must> be quoted in order to correctly
+parse as the intended version, especially when using the C<declare> or
+L</qv()> methods. While you do not have to quote decimal numbers when
+creating version objects, it is always safe to quote B<all> initial values
+when using version.pm methods, as this will ensure that what you type is
+what is used.
+
+Additionally, if you quote your initializer, then the quoted value that goes
+B<in> will be exactly what comes B<out> when your $VERSION is printed
+(stringified). If you do not quote your value, Perl's normal numeric handling
+comes into play and you may not get back what you were expecting.
+
+If you use a mathematic formula that resolves to a floating point number,
+you are dependent on Perl's conversion routines to yield the version you
+expect. You are pretty safe by dividing by a power of 10, for example,
+but other operations are not likely to be what you intend. For example:
+
+ $VERSION = version->new((qw$Revision: 1.4)[1]/10);
+ print $VERSION; # yields 0.14
+ $V2 = version->new(100/9); # Integer overflow in decimal number
+ print $V2; # yields something like 11.111.111.100
+
+Perl 5.8.1 and beyond are able to automatically quote v-strings but
+that is not possible in earlier versions of Perl. In other words:
+
+ $version = version->new("v2.5.4"); # legal in all versions of Perl
+ $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
+
+=head2 What about v-strings?
+
+There are two ways to enter v-strings: a bare number with two or more
+decimal points, or a bare number with one or more decimal points and a
+leading 'v' character (also bare). For example:
+
+ $vs1 = 1.2.3; # encoded as \1\2\3
+ $vs2 = v1.2; # encoded as \1\2
+
+However, the use of bare v-strings to initialize version objects is
+B<strongly> discouraged in all circumstances. Also, bare
+v-strings are not completely supported in any version of Perl prior to
+5.8.1.
+
+If you insist on using bare v-strings with Perl > 5.6.0, be aware of the
+following limitations:
+
+1) For Perl releases 5.6.0 through 5.8.0, the v-string code merely guesses,
+based on some characteristics of v-strings. You B<must> use a three part
+version, e.g. 1.2.3 or v1.2.3 in order for this heuristic to be successful.
+
+2) For Perl releases 5.8.1 and later, v-strings have changed in the Perl
+core to be magical, which means that the version.pm code can automatically
+determine whether the v-string encoding was used.
+
+3) In all cases, a version created using v-strings will have a stringified
+form that has a leading 'v' character, for the simple reason that sometimes
+it is impossible to tell whether one was present initially.
+
+=head2 Version Object Internals
+
+version.pm provides an overloaded version object that is designed to both
+encapsulate the author's intended $VERSION assignment as well as make it
+completely natural to use those objects as if they were numbers (e.g. for
+comparisons). To do this, a version object contains both the original
+representation as typed by the author, as well as a parsed representation
+to ease comparisons. Version objects employ L<overload> methods to
+simplify code that needs to compare, print, etc the objects.
+
+The internal structure of version objects is a blessed hash with several
+components:
+
+ bless( {
+ 'original' => 'v1.2.3_4',
+ 'alpha' => 1,
+ 'qv' => 1,
+ 'version' => [
+ 1,
+ 2,
+ 3,
+ 4
+ ]
+ }, 'version' );
+
+=over 4
+
+=item original
+
+A faithful representation of the value used to initialize this version
+object. The only time this will not be precisely the same characters
+that exist in the source file is if a short dotted-decimal version like
+v1.2 was used (in which case it will contain 'v1.2'). This form is
+B<STRONGLY> discouraged, in that it will confuse you and your users.
+
+=item qv
+
+A boolean that denotes whether this is a decimal or dotted-decimal version.
+See L<version/is_qv()>.
+
+=item alpha
+
+A boolean that denotes whether this is an alpha version. NOTE: that the
+underscore can only appear in the last position. See L<version/is_alpha()>.
+
+=item version
+
+An array of non-negative integers that is used for comparison purposes with
+other version objects.
+
+=back
+
+=head2 Replacement UNIVERSAL::VERSION
+
+In addition to the version objects, this modules also replaces the core
+UNIVERSAL::VERSION function with one that uses version objects for its
+comparisons. The return from this operator is always the stringified form
+as a simple scalar (i.e. not an object), but the warning message generated
+includes either the stringified form or the normal form, depending on how
+it was called.
+
+For example:
+
+ package Foo;
+ $VERSION = 1.2;
+
+ package Bar;
+ $VERSION = "v1.3.5"; # works with all Perl's (since it is quoted)
+
+ package main;
+ use version;
+
+ print $Foo::VERSION; # prints 1.2
+
+ print $Bar::VERSION; # prints 1.003005
+
+ eval "use foo 10";
+ print $@; # prints "foo version 10 required..."
+ eval "use foo 1.3.5; # work in Perl 5.6.1 or better
+ print $@; # prints "foo version 1.3.5 required..."
+
+ eval "use bar 1.3.6";
+ print $@; # prints "bar version 1.3.6 required..."
+ eval "use bar 1.004"; # note Decimal version
+ print $@; # prints "bar version 1.004 required..."
+
+
+IMPORTANT NOTE: This may mean that code which searches for a specific
+string (to determine whether a given module is available) may need to be
+changed. It is always better to use the built-in comparison implicit in
+C<use> or C<require>, rather than manually poking at C<< class->VERSION >>
+and then doing a comparison yourself.
+
+The replacement UNIVERSAL::VERSION, when used as a function, like this:
+
+ print $module->VERSION;
+
+will also exclusively return the stringified form. See L</Stringification>
+for more details.
+
+=head1 USAGE DETAILS
+
+=head2 Using modules that use version.pm
+
+As much as possible, the version.pm module remains compatible with all
+current code. However, if your module is using a module that has defined
+C<$VERSION> using the version class, there are a couple of things to be
+aware of. For purposes of discussion, we will assume that we have the
+following module installed:
+
+ package Example;
+ use version; $VERSION = qv('1.2.2');
+ ...module code here...
+ 1;
+
+=over 4
+
+=item Decimal versions always work
+
+Code of the form:
+
+ use Example 1.002003;
+
+will always work correctly. The C<use> will perform an automatic
+C<$VERSION> comparison using the floating point number given as the first
+term after the module name (e.g. above 1.002.003). In this case, the
+installed module is too old for the requested line, so you would see an
+error like:
+
+ Example version 1.002003 (v1.2.3) required--this is only version 1.002002 (v1.2.2)...
+
+=item Dotted-Decimal version work sometimes
+
+With Perl >= 5.6.2, you can also use a line like this:
+
+ use Example 1.2.3;
+
+and it will again work (i.e. give the error message as above), even with
+releases of Perl which do not normally support v-strings (see L<What about v-strings?> above). This has to do with that fact that C<use> only checks
+to see if the second term I<looks like a number> and passes that to the
+replacement L<UNIVERSAL::VERSION|UNIVERSAL/VERSION>. This is not true in Perl 5.005_04,
+however, so you are B<strongly encouraged> to always use a Decimal version
+in your code, even for those versions of Perl which support the Dotted-Decimal
+version.
+
+=back
+
+=head2 Object Methods
+
+=over 4
+
+=item new()
+
+Like many OO interfaces, the new() method is used to initialize version
+objects. If two arguments are passed to C<new()>, the B<second> one will be
+used as if it were prefixed with "v". This is to support historical use of the
+C<qw> operator with the CVS variable $Revision, which is automatically
+incremented by CVS every time the file is committed to the repository.
+
+In order to facilitate this feature, the following
+code can be employed:
+
+ $VERSION = version->new(qw$Revision: 2.7 $);
+
+and the version object will be created as if the following code
+were used:
+
+ $VERSION = version->new("v2.7");
+
+In other words, the version will be automatically parsed out of the
+string, and it will be quoted to preserve the meaning CVS normally
+carries for versions. The CVS $Revision$ increments differently from
+Decimal versions (i.e. 1.10 follows 1.9), so it must be handled as if
+it were a Dotted-Decimal Version.
+
+A new version object can be created as a copy of an existing version
+object, either as a class method:
+
+ $v1 = version->new(12.3);
+ $v2 = version->new($v1);
+
+or as an object method:
+
+ $v1 = version->new(12.3);
+ $v2 = $v1->new(12.3);
+
+and in each case, $v1 and $v2 will be identical. NOTE: if you create
+a new object using an existing object like this:
+
+ $v2 = $v1->new();
+
+the new object B<will not> be a clone of the existing object. In the
+example case, $v2 will be an empty object of the same type as $v1.
+
+=back
+
+=over 4
+
+=item qv()
+
+An alternate way to create a new version object is through the exported
+qv() sub. This is not strictly like other q? operators (like qq, qw),
+in that the only delimiters supported are parentheses (or spaces). It is
+the best way to initialize a short version without triggering the floating
+point interpretation. For example:
+
+ $v1 = qv(1.2); # v1.2.0
+ $v2 = qv("1.2"); # also v1.2.0
+
+As you can see, either a bare number or a quoted string can usually
+be used interchangeably, except in the case of a trailing zero, which
+must be quoted to be converted properly. For this reason, it is strongly
+recommended that all initializers to qv() be quoted strings instead of
+bare numbers.
+
+To prevent the C<qv()> function from being exported to the caller's namespace,
+either use version with a null parameter:
+
+ use version ();
+
+or just require version, like this:
+
+ require version;
+
+Both methods will prevent the import() method from firing and exporting the
+C<qv()> sub.
+
+=back
+
+For the subsequent examples, the following three objects will be used:
+
+ $ver = version->new("1.2.3.4"); # see "Quoting Rules"
+ $alpha = version->new("1.2.3_4"); # see "Alpha Versions"
+ $nver = version->new(1.002); # see "Decimal Versions"
+
+=over 4
+
+=item Normal Form
+
+For any version object which is initialized with multiple decimal
+places (either quoted or if possible v-string), or initialized using
+the L<qv()|version/qv()> operator, the stringified representation is returned in
+a normalized or reduced form (no extraneous zeros), and with a leading 'v':
+
+ print $ver->normal; # prints as v1.2.3.4
+ print $ver->stringify; # ditto
+ print $ver; # ditto
+ print $nver->normal; # prints as v1.2.0
+ print $nver->stringify; # prints as 1.002,
+ # see "Stringification"
+
+In order to preserve the meaning of the processed version, the
+normalized representation will always contain at least three sub terms.
+In other words, the following is guaranteed to always be true:
+
+ my $newver = version->new($ver->stringify);
+ if ($newver eq $ver ) # always true
+ {...}
+
+=back
+
+=over 4
+
+=item Numification
+
+Although all mathematical operations on version objects are forbidden
+by default, it is possible to retrieve a number which corresponds
+to the version object through the use of the $obj->numify
+method. For formatting purposes, when displaying a number which
+corresponds a version object, all sub versions are assumed to have
+three decimal places. So for example:
+
+ print $ver->numify; # prints 1.002003004
+ print $nver->numify; # prints 1.002
+
+Unlike the stringification operator, there is never any need to append
+trailing zeros to preserve the correct version value.
+
+=back
+
+=over 4
+
+=item Stringification
+
+The default stringification for version objects returns exactly the same
+string as was used to create it, whether you used C<new()> or C<qv()>,
+with one exception. The sole exception is if the object was created using
+C<qv()> and the initializer did not have two decimal places or a leading
+'v' (both optional), then the stringified form will have a leading 'v'
+prepended, in order to support round-trip processing.
+
+For example:
+
+ Initialized as Stringifies to
+ ============== ==============
+ version->new("1.2") 1.2
+ version->new("v1.2") v1.2
+ qv("1.2.3") 1.2.3
+ qv("v1.3.5") v1.3.5
+ qv("1.2") v1.2 ### exceptional case
+
+See also L<UNIVERSAL::VERSION|UNIVERSAL/VERSION>, as this also returns the stringified form
+when used as a class method.
+
+IMPORTANT NOTE: There is one exceptional cases shown in the above table
+where the "initializer" is not stringwise equivalent to the stringified
+representation. If you use the C<qv>() operator on a version without a
+leading 'v' B<and> with only a single decimal place, the stringified output
+will have a leading 'v', to preserve the sense. See the L</qv()> operator
+for more details.
+
+IMPORTANT NOTE 2: Attempting to bypass the normal stringification rules by
+manually applying L<numify()|version/numify()> and L<normal()|version/normal()> will sometimes yield
+surprising results:
+
+ print version->new(version->new("v1.0")->numify)->normal; # v1.0.0
+
+The reason for this is that the L<numify()|version/numify()> operator will turn "v1.0"
+into the equivalent string "1.000000". Forcing the outer version object
+to L<normal()|version/normal()> form will display the mathematically equivalent "v1.0.0".
+
+As the example in L</new()> shows, you can always create a copy of an
+existing version object with the same value by the very compact:
+
+ $v2 = $v1->new($v1);
+
+and be assured that both C<$v1> and C<$v2> will be completely equivalent,
+down to the same internal representation as well as stringification.
+
+=back
+
+=over 4
+
+=item Comparison operators
+
+Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between
+terms (upgrading to a version object automatically). Perl automatically
+generates all of the other comparison operators based on those two.
+In addition to the obvious equalities listed below, appending a single
+trailing 0 term does not change the value of a version for comparison
+purposes. In other words "v1.2" and "1.2.0" will compare as identical.
+
+For example, the following relations hold:
+
+ As Number As String Truth Value
+ ------------- ---------------- -----------
+ $ver > 1.0 $ver gt "1.0" true
+ $ver < 2.5 $ver lt true
+ $ver != 1.3 $ver ne "1.3" true
+ $ver == 1.2 $ver eq "1.2" false
+ $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below
+
+It is probably best to chose either the Decimal notation or the string
+notation and stick with it, to reduce confusion. Perl6 version objects
+B<may> only support Decimal comparisons. See also L<Quoting Rules>.
+
+WARNING: Comparing version with unequal numbers of decimal points (whether
+explicitly or implicitly initialized), may yield unexpected results at
+first glance. For example, the following inequalities hold:
+
+ version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
+ version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
+
+For this reason, it is best to use either exclusively L<Decimal Versions> or
+L<Dotted-Decimal Versions> with multiple decimal points.
+
+=back
+
+=over 4
+
+=item Logical Operators
+
+If you need to test whether a version object
+has been initialized, you can simply test it directly:
+
+ $vobj = version->new($something);
+ if ( $vobj ) # true only if $something was non-blank
+
+You can also test whether a version object is an alpha version, for
+example to prevent the use of some feature not present in the main
+release:
+
+ $vobj = version->new("1.2_3"); # MUST QUOTE
+ ...later...
+ if ( $vobj->is_alpha ) # True
+
+=back
+
+=head1 AUTHOR
+
+John Peacock E<lt>jpeacock@cpan.orgE<gt>
+
+=head1 SEE ALSO
+
+L<perl>.
+
+=cut
diff --git a/systems/texlive/tlnet/tlpkg/tlperl/lib/version/regex.pm b/systems/texlive/tlnet/tlpkg/tlperl/lib/version/regex.pm
new file mode 100644
index 0000000000..4e44d12c93
--- /dev/null
+++ b/systems/texlive/tlnet/tlpkg/tlperl/lib/version/regex.pm
@@ -0,0 +1,115 @@
+package version::regex;
+
+use strict;
+
+our $VERSION = 0.9923;
+
+#--------------------------------------------------------------------------#
+# Version regexp components
+#--------------------------------------------------------------------------#
+
+# Fraction part of a decimal version number. This is a common part of
+# both strict and lax decimal versions
+
+my $FRACTION_PART = qr/\.[0-9]+/;
+
+# First part of either decimal or dotted-decimal strict version number.
+# Unsigned integer with no leading zeroes (except for zero itself) to
+# avoid confusion with octal.
+
+my $STRICT_INTEGER_PART = qr/0|[1-9][0-9]*/;
+
+# First part of either decimal or dotted-decimal lax version number.
+# Unsigned integer, but allowing leading zeros. Always interpreted
+# as decimal. However, some forms of the resulting syntax give odd
+# results if used as ordinary Perl expressions, due to how perl treats
+# octals. E.g.
+# version->new("010" ) == 10
+# version->new( 010 ) == 8
+# version->new( 010.2) == 82 # "8" . "2"
+
+my $LAX_INTEGER_PART = qr/[0-9]+/;
+
+# Second and subsequent part of a strict dotted-decimal version number.
+# Leading zeroes are permitted, and the number is always decimal.
+# Limited to three digits to avoid overflow when converting to decimal
+# form and also avoid problematic style with excessive leading zeroes.
+
+my $STRICT_DOTTED_DECIMAL_PART = qr/\.[0-9]{1,3}/;
+
+# Second and subsequent part of a lax dotted-decimal version number.
+# Leading zeroes are permitted, and the number is always decimal. No
+# limit on the numerical value or number of digits, so there is the
+# possibility of overflow when converting to decimal form.
+
+my $LAX_DOTTED_DECIMAL_PART = qr/\.[0-9]+/;
+
+# Alpha suffix part of lax version number syntax. Acts like a
+# dotted-decimal part.
+
+my $LAX_ALPHA_PART = qr/_[0-9]+/;
+
+#--------------------------------------------------------------------------#
+# Strict version regexp definitions
+#--------------------------------------------------------------------------#
+
+# Strict decimal version number.
+
+our $STRICT_DECIMAL_VERSION =
+ qr/ $STRICT_INTEGER_PART $FRACTION_PART? /x;
+
+# Strict dotted-decimal version number. Must have both leading "v" and
+# at least three parts, to avoid confusion with decimal syntax.
+
+our $STRICT_DOTTED_DECIMAL_VERSION =
+ qr/ v $STRICT_INTEGER_PART $STRICT_DOTTED_DECIMAL_PART{2,} /x;
+
+# Complete strict version number syntax -- should generally be used
+# anchored: qr/ \A $STRICT \z /x
+
+our $STRICT =
+ qr/ $STRICT_DECIMAL_VERSION | $STRICT_DOTTED_DECIMAL_VERSION /x;
+
+#--------------------------------------------------------------------------#
+# Lax version regexp definitions
+#--------------------------------------------------------------------------#
+
+# Lax decimal version number. Just like the strict one except for
+# allowing an alpha suffix or allowing a leading or trailing
+# decimal-point
+
+our $LAX_DECIMAL_VERSION =
+ qr/ $LAX_INTEGER_PART (?: $FRACTION_PART | \. )? $LAX_ALPHA_PART?
+ |
+ $FRACTION_PART $LAX_ALPHA_PART?
+ /x;
+
+# Lax dotted-decimal version number. Distinguished by having either
+# leading "v" or at least three non-alpha parts. Alpha part is only
+# permitted if there are at least two non-alpha parts. Strangely
+# enough, without the leading "v", Perl takes .1.2 to mean v0.1.2,
+# so when there is no "v", the leading part is optional
+
+our $LAX_DOTTED_DECIMAL_VERSION =
+ qr/
+ v $LAX_INTEGER_PART (?: $LAX_DOTTED_DECIMAL_PART+ $LAX_ALPHA_PART? )?
+ |
+ $LAX_INTEGER_PART? $LAX_DOTTED_DECIMAL_PART{2,} $LAX_ALPHA_PART?
+ /x;
+
+# Complete lax version number syntax -- should generally be used
+# anchored: qr/ \A $LAX \z /x
+#
+# The string 'undef' is a special case to make for easier handling
+# of return values from ExtUtils::MM->parse_version
+
+our $LAX =
+ qr/ undef | $LAX_DOTTED_DECIMAL_VERSION | $LAX_DECIMAL_VERSION /x;
+
+#--------------------------------------------------------------------------#
+
+# Preloaded methods go here.
+sub is_strict { defined $_[0] && $_[0] =~ qr/ \A $STRICT \z /x }
+sub is_lax { defined $_[0] && $_[0] =~ qr/ \A $LAX \z /x }
+
+1;