In case you may be interested, List::Compare provides a means of getting the intersection of two lists. In addition to it being well designed, it will only return a list of unique elements--in case either list has repeating elements.

For example, modify Don Coyote's data to the following:

file1
-----
one
two
three
four
five

six
seven
eight

file2
-----
five
five
five

six
seven
eight
nine
ten
eleven
twelve

[download]

And run the following on it:

#!/usr/bin/perl -w
use strict;
use warnings;
use List::Compare;

@ARGV == 2 or die 'Error: Two files needed for comparison.';

open my $inA, '<', $ARGV[0] or die qq{Unable to open file "$ARGV[0]": 
+$!};
chomp( my @nomi = <$inA> );
close $inA;

open my $inB, '<', $ARGV[1] or die qq{Unable to open file "$ARGV[1]": 
+$!};
chomp( my @indirizzi = <$inB> );
close $inB;

my $lc = List::Compare->new(\@nomi, \@indirizzi);

my @intersection = $lc->get_intersection;

print "$_\n" for @intersection;

[download]

Here's the output:

eight
five
seven
six

[download]

In reply to Re: Foreach loop explanation by Kenosis
in thread Foreach loop explanation by ananassa

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