List lines in file A but not in file B

I found this interesting scripts' page: http://tkhanson.net/misc/ and I think that I got an alternative to the anb script:

#!/usr/bin/perl

use strict;

use warnings;

sub usage {

        print "$0: filea fileb\n";

        exit -1;

}

usage unless scalar @ARGV == 2;

my $a = shift @ARGV;

my $b = shift @ARGV;

open A, "<$a" or die "can't open $a: $!\n";

open B, "<$b" or die "can't open $b: $!\n";

my %bl;

$bl{$_}++ for (<B>);

for (<A>) {print "$_" unless $bl{$_}};

__END__

Or using map for the last lines:

my %bl = map {$_ => 1 } (<B>);

map {print "$_" unless $bl{$_}} (<A>);

TIMTOWTDI