use strict;
use warnings;

my @array1 = qw( c d e );
my @array2 = qw( e f g h );
my @array3 = qw( a b d );
my @array4 = qw( s g h j k l );

open my $out, '>', 'output' or die "Cannot open: $!\n";

foreach my $a1 ( \@array1, \@array2, \@array3, \@array4 ) {
    foreach my $a2 ( \@array1, \@array2, \@array3, \@array4 ) {
        my ( %union, %intersect );
        foreach my $item1 ( @$a1 ) {
            foreach my $item2 ( @$a2 ) {
                # print "item1: $item1\nitem2: $item2\n";
                $union{$item1}++;
                $union{$item2}++;
                if ( $item1 eq $item2 ) {
                    $intersect{$item1}++;
                }
            }
        }
        my @intersect = sort keys %intersect;
        print $out "@intersect\n"; #prints intersecting words
        print $out scalar @intersect . "\n";
    }
}

close $out or die "Error closing output; $!\n";