This works whether the arrays contain duplicate elements or not:

my %a = map { $_ => 1 } @a;
my %b = map { $_ => 1 } @b;

@c = grep { !$b{$_} } @a;
@d = grep { !$a{$_} } @b;
[download]

Please look again. This is not the elimination of duplicates.

oops, you're right. I can't figure out what the pattern is. What does he mean by "canceling out"?

Update: Here's a solution:

use Math::BigInt       ();
use Math::Big::Factors ();

my $a = Math::BigInt->new(1);
$a *= $_ foreach @a;  # 17820000

my $b = Math::BigInt->new(1);
$b *= $_ foreach @b;  # 19872000

my $gcd = Math::BigInt::bgcd($a, $b);  # 108000

my $c = $a / $gcd;  # 165
my $d = $b / $gcd;  # 184

my @c = Math::Big::Factors::factors_wheel($c);  # 3, 5, 11
my @d = Math::Big::Factors::factors_wheel($d);  # 2, 2, 2, 23
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Not quite the solution you asked for. Close enough?

Is this a factoring problem? Math::Factor and Math::Big::Factors may have useful routines. In particular Math::Factor has the subroutine "match" that sounds something like what you're trying to do, though as others have stated, it's still not clear what exactly that is.

-xdg

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