$ perl -MRegexp::Common=net -wle 'print $RE{net}{IPv4}'
(?:(?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2}))

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

my $line = ('a' x 500) . 'b!' . ('a' x 20);

use Benchmark qw( cmpthese );

cmpthese -3, {
    literal => sub {$line =~ /a.{1,10}b!/ },
    class   => sub {$line =~ /a.{1,10}[b][!]/},
};
__END__
            Rate   class literal
class     3855/s      --    -99%
literal 712766/s  18390%      --