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

my @choices = qw|a b c|;

my %choices = map{$_=>1}@choices;

my @cData = <DATA>;

timethese(100000,{'Damn Slow'=>\&parseData1,
                'Much Better'=>\&parseData2});

sub parseData1 {
foreach (@cData){
chomp;
my @items = split/,/,$_;
#slow way, 
foreach my $item (@items){
if(grep {$item eq $_} @choices){
   #print qq|FOUND $item|;
 } 
}

}
}

sub parseData2 {
 foreach(@cData){
 chomp;
 foreach my $item (split/,/,$_){
    if ($choices{$item}){
       #print qq|FOUND $item\n|;
     }
   }
  }

}

__DATA__
z,t,m,u,a,b,c
s,t,l,m,z,a,s
c,b,a,m,u,t,n
k,l,t,s,z,r,t


##</code><code>##

Benchmark: timing 100000 iterations of Damn Slow, Much Better...
 Damn Slow:  9 wallclock secs ( 8.81 usr +  0.00 sys =  8.81 CPU) @ 11348.16/s
n=100000)
Much Better:  4 wallclock secs ( 3.88 usr +  0.00 sys =  3.88 CPU) @ 25806.45/s
(n=100000)