Here's the canonical WTDI:

#!/perl/bin/perl

use strict;
use warnings;

my @arrA = qw/ 1 3 5 7 9 11 13 /;
my @arrB = qw/ 1 4 9 16 25 /;

my %hashB = map { $_ => 1 } @arrB; # Hashify the B array for later com
+parison

print qq(These numbers are in array A:\n);
print join("  ", @arrA);
print "\n\n";

print qq(These numbers are in array B:\n);
print join("  ", @arrB);
print "\n\n";

print qq(These numbers are in array A, but not array B:\n);
for my $curA (@arrA) {
  unless (exists($hashB{$curA})) {
    print "  $curA";
  }
}
print "\n\n";
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Output:

These numbers are in array A:
1  3  5  7  9  11  13

These numbers are in array B:
1  4  9  16  25

These numbers are in array A, but not array B:
  3  5  7  11  13
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