I used this script for benchmarking:

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw(:all);


my $grinder = sub {
    for (0 .. 1000){
        if ("$_" =~ m/^(?:2(?:[6-9]|5[0-5]?|[0-4]\d?)?|[3-9]\d?|1(?:\d
+\d?)?|0)$/){
            if ($_ > 255){
                print "Fails for $_\n";
            } 
        } else {
            if ($_ < 255){
                print "Fails for $_\n";
            }
        }
    }
};

my $mwah = sub {
    my $re = qr{
            ((?>\d+))            # what to capture, don't backtrack: (
++?> )
            (??{
                $1<255           # what is looked for
                ? ''             # if yes, let the regex succeed
                : '(?!)'         # if no, let the regex bail
            }) 
          }x;
    for (0 .. 1000){
        if ("$_" =~ m/^$re$/){
            if ($_ > 255){
                print "Fails for $_\n";
            } 
        } else {
            if ($_ < 255){
                print "Fails for $_\n";
            }
        }
    }
};

my $bruteforce = sub {
    my $re = join '|', 0 .. 255;
#    print $re, "\n";
    for (0 .. 1000){
        if ("$_" =~ m{^(?:$re)$}){
            if ($_ > 255){
                print "Brute force Fails for $_\n";
            } 
        } else {
            if ($_ < 255){
                print "Brute force Fails for $_\n";
            }
        }
    }
};

cmpthese(-3, {
        grinder        => $grinder,
        mwah        => $mwah,
        brute_force    => $bruteforce,
        });
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