If you want to compare arrays there are more efficient ways. But to expand on grep{} in a list context, you can put anything you want inside the grep. If the *last line* in the grep is "true" then input is passed to the output.

Here is a simple example where what is in the grep{} has nothing to do with the input list...an odd/even flip-flopper. Perl grep can do some very cool things that command line grep can't!

#!/usr/bin/perl -w
use strict;

my @test = qw (a b c d e f);
my $is_even_flag =1;

my @odd_tests = grep {$is_even_flag ^= 1;
                     }@test;
print "@odd_tests";  

#prints b d f
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