#!/usr/bin/perl
use strict;
use warnings;
 
use Benchmark 'cmpthese';
use List::Util 'first';
 
my @words = qw[ new old number start simple cross heavy die exit ];
my $string = join ' 0\4/f ', map( { rand $_ } 1 .. 60), map { $words[ rand @words ] } 1 .. 20;
 
cmpthese (-3, {
        regexp => sub {
            return $string =~ /(new|old|number|start|simple|cross|heavy|die|exit)/i;
        },
        use_index => sub {
            my $lcstring = lc $string;
            return first {index($lcstring, $_) > -1} @words;
        }
});

__END__
             Rate    regexp use_index
regexp     1084/s        --      -96%
use_index 29469/s     2619%        --