This example shows that the main speed difference is reall Regexp::Common, which does a bit more than just match \d{1,3}\.\d{1,3}\. ..: 
$ 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}))

[download]
The optimzation I talked about kicks in when the string is much longer, and the literal char occurs only once or twice. Then the literal is used as an anchor, thus reducing the need for backtracking. 
#!/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%      --

[download]

Update: added benchmark

In reply to Re^6: Sort/Uniq Help by moritz
in thread Sort/Uniq Help by learningperl01

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