#!perl -w
use strict;

use Benchmark qw/:all/;

my $result = timethese( -5, {
                index => sub { -1 != index 'fooabc123', '123' },
                regex => sub { 'fooabc123' =~ /123/ }
             } );
cmpthese $result;
[download]

Benchmark: running index, regex for at least 5 CPU seconds...
     index:  6 wallclock secs ( 6.56 usr + -0.03 sys =  6.53 CPU) @ 81
+19742.77/s
 (n=53030040)
     regex:  5 wallclock secs ( 5.50 usr +  0.00 sys =  5.50 CPU) @ 44
+81230.91/s
 (n=24646770)
           Rate regex index
regex 4481231/s    --  -45%
index 8119743/s   81%    --
[download]

#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use Benchmark qw/:all/;

sub LCSRegEx {
    my $substr = $_[0];
    my $len = length $_[0];
    my $off = 0;
    while ($substr) {
        my @matches = grep /\Q$substr/, @_;
        last if @matches == @_;
        $off++;
        $len-- and $off=0 if $off+$len > length $_[0];
        $substr = substr $_[0], $off, $len;
    }
    return $substr;
}

sub LCSIndex {
    my $substr = $_[0];
    my $len = length $_[0];
    my $off = 0;
    while ($substr) {
        my @matches = grep { -1 != index $_, $substr } @_;
        last if @matches == @_;
        $off++;
        $len-- and $off=0 if $off+$len > length $_[0];
        $substr = substr $_[0], $off, $len;
    }
    return $substr;
}

my $result = timethese( -5, {
   LCSRegEx => sub {
      for ([ qw(fooabc123 fooabc321 foobca232) ],
           [ qw(abcfoo123 bcafoo321 foo123abc) ],
           [ qw(foo bor boz bzo) ]) {
         LCSRegEx(@{$_});
      }
   },
   LCSIndex => sub {
      for ([ qw(fooabc123 fooabc321 foobca232) ],
           [ qw(abcfoo123 bcafoo321 foo123abc) ],
           [ qw(foo bor boz bzo) ]) {
         LCSIndex(@{$_});
      }
   }
});
cmpthese $result;
[download]

Benchmark: running LCSIndex, LCSRegEx for at least 5 CPU seconds...
  LCSIndex:  6 wallclock secs ( 5.28 usr +  0.00 sys =  5.28 CPU) @ 34
+63.93/s (n
=18293)
  LCSRegEx:  6 wallclock secs ( 5.50 usr +  0.00 sys =  5.50 CPU) @ 91
+6.36/s (n=
5040)
           Rate LCSRegEx LCSIndex
LCSRegEx  916/s       --     -74%
LCSIndex 3464/s     278%       --
[download]