#!/usr/bin/perl -w
use strict;
$|++;

use Benchmark;

my $string  = 'cat';
my $search  = 'c';
my $replace = 'b';

timethese( 1000000, {
                  Eval => sub { eval "$string =~ tr/$search/$replace/" },
                  S_op => sub { $string =~ s/$search/$replace/g },
                 }
          );