#!/usr/local/bin/perl -w

use strict;
use Benchmark;

my $i = 34;

timethese(3000000, {
 AND=>\&and_them,
 MOD=>\&mod_them,
 NULL_LOOP=>\&null_loop,
});

sub null_loop {
}

sub and_them {
 $i & 1;
}

sub mod_them {
 $i % 2;
}
~
"tst" 23 lines, 229 characters 
[rover:DEV]~/tst>./tst
Benchmark: 
timing 3000000 iterations of
 AND, MOD, NULL_LOOP
...

       AND:  1 wallclock secs ( 1.68 usr +  0.00 sys =  1.68 CPU) @ 1785714.29/s (n=3000000)

       MOD:  2 wallclock secs ( 2.33 usr +  0.00 sys =  2.33 CPU) @ 1287553.65/s (n=3000000)

 NULL_LOOP: -1 wallclock secs (-0.07 usr +  0.00 sys = -0.07 CPU) @ -42857142.86/s (n=3000000)

            (warning: too few iterations for a reliable count)