`
``
use Sort::Versions;
@l = sort { versioncmp($a, $b) } qw( 1.2 1.2.0 1.2a.0 1.2.a 1.a 02.a );
...
use Sort::Versions;
print lower if versioncmp(1.2, 1.2a) == -1;
...
use Sort::Versions;
%h = (1 => d, 2 => c, 3 => b, 4 => a);
@h = sort { versioncmp($h{$a}, $h{$b}) } keys %h;
`

Sort::Versions allows easy sorting of mixed non-numeric and numeric strings,
like the ’version numbers’ that many shared library systems and revision
control packages use. This is quite useful if you are trying to deal with
shared libraries. It can also be applied to applications that intersperse
variable-width numeric fields within text. Other applications can
undoubtedly be found.
For an explanation of the algorithm, it’s simplest to look at these examples:

`
`

`
1.1 < 1.2
1.1a < 1.2
1.1 < 1.1.1
1.1 < 1.1a
1.1.a < 1.1a
1 < a
a < b
1 < 2
1.1-3 < 1.1-4
1.1-5 < 1.1.6
`

More precisely (but less comprehensibly), the two strings are treated
as subunits delimited by periods or hyphens. Each subunit can contain
any number of groups of digits or non-digits. If digit groups are
being compared on both sides, a numeric comparison is used, otherwise
a ASCII ordering is used. A group or subgroup with more units will win
if all comparisons are equal. A period binds digit groups together
more tightly than a hyphen.

Some packages use a different style of version numbering: a simple
real number written as a decimal. Sort::Versions has limited support
for this style: when comparing two subunits which are both digit
groups, if either subunit has a leading zero, then both are treated
like digits after a decimal point. So for example:

`
`

`
0002 < 1
1.06 < 1.5
`

This won’t always work, because there won’t always be a leading zero
in real-number style version numbers. There is no way for
Sort::Versions to know which style was intended. But a lot of the time
it will do the right thing. If you are making up version numbers, the
style with (possibly) more than one dot is the style to use.