From perldata:

Version Strings

Note: Version Strings (v-strings) have been deprecated. They will be removed in some future release after Perl 5.8.1. The marginal benefits of v-strings were greatly outweighed by the potential for Surprise and Confusion.

A literal of the form v1.20.300.4000 is parsed as a string composed of characters with the specified ordinals. This form, known as v-strings, provides an alternative, more readable way to construct strings, rather than use the somewhat less readable interpolation form "\x{1}\x{14}\x{12c}\x{fa0}". This is useful for representing Unicode strings, and for comparing version "numbers" using the string comparison operators, cmp, gt, lt etc. If there are two or more dots in the literal, the leading v may be omitted.

    print v9786;              # prints SMILEY, "\x{263a}"
    print v102.111.111;       # prints "foo"
    print 102.111.111;        # same

Such literals are accepted by both require and use for doing a version check. Note that using the v-strings for IPv4 addresses is not portable unless you also use the inet_aton()/inet_ntoa() routines of the Socket package.

Note that since Perl 5.8.1 the single-number v-strings (like v65 ) are not v-strings before the => operator (which is usually used to separate a hash key from a hash value), instead they are interpreted as literal strings ('v65'). They were v-strings from Perl 5.6.0 to Perl 5.8.0, but that caused more confusion and breakage than good. Multi-number v-strings like v65.66 and 65.66.67 continue to be v-strings always.

Version strings are not meant to be used for IP addresses.

Version strings are not meant to be used for IP addresses.

In fact, I think they were... Not that you should ever actually use them.

use strict;
use warnings;
use Socket;

my $perlmonks1 = inet_aton("66.39.54.27");
my $perlmonks2 = v66.39.54.27;

print "Holy crap, this really works?\n" if $perlmonks1 eq $perlmonks2;
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And atually, yes, it does work for values higher than 127...

for my $IP (qw(66.39.54.27 209.197.123.153 208.159.114.4)) {
    my $perlmonks1 = inet_aton($IP);
    my $perlmonks2 = eval qq{ v$IP } or die $@;

    print "Holy crap, this really works ($IP)?\n" if $perlmonks1 eq $p
+erlmonks2;
}
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-Paul

How do you morph "Version Strings" into "meant to be used for IP addresses"?

for (
    [ 127, v4.127 ],
    [ 128, v4.128 ],
    [ 160, v4.160 ],
    [ 194, v4.194 ],
) {
    my ($x, $vstr) = @$_;

    # Workaround
    utf8::downgrade(my $vstr_dn = $vstr);

    printf(
        "got: %04X   " .
        "workaround: %04X   " .
        "expecting: 04%3\$02X or %3\$02X04\n",

        unpack('S', $vstr),
        unpack('S', $vstr_dn),
        $x,
    );
}
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< 5.10.0:

got: 7F04   workaround: 7F04   expecting: 047F or 7F04
got: C204   workaround: 8004   expecting: 0480 or 8004
got: C204   workaround: A004   expecting: 04A0 or A004
got: C304   workaround: C204   expecting: 04C2 or C204
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≥ 5.10.0:

got: 7F04   workaround: 7F04   expecting: 047F or 7F04
got: 8004   workaround: 8004   expecting: 0480 or 8004
got: A004   workaround: A004   expecting: 04A0 or A004
got: C204   workaround: C204   expecting: 04C2 or C204
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Before 5.10.0, unpack used the internal buffer of its inputs with no regards to how the string was encoded within that buffer.