#!/usr/bin/perl
use strict;
use warnings;
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS
# use Benchmark qw(:all) ; # WindowsOS

my @preserved = @ARGV;

sub test_grep {
    @ARGV = @preserved; # restore original @ARGV
    my @matched = grep { $_ =~ /AGGT/ } <>;

    my $count;
    if (@matched) {
	for(@matched) { chomp $_; $count .= length($_) . " ";}
    }
    close ARGV if eof;
}

sub test_while {
    @ARGV = @preserved; # restore original @ARGV
    my $count;
    while (<>) {
	if ($_ =~ /AGGT/){
	    chomp;
	    $count .= length($_) . " ";
	}
    } continue {
	close ARGV if eof; # reset $. each file
    }
}

my $results = timethese(10000000, { Grep => \&test_grep,
				    While => \&test_while }, 'none');
cmpthese( $results );

__DATA__

 perl test.pl test.txt
          Rate  Grep While
Grep  144175/s    --  -21%
While 182882/s   27%    --