The expression @quantity = [2,1] does not assign two values into the array, it instead assigns an anonymous array reference which contains two values into the array. Did you mean @quantity = (2,1) instead? Here is some more code to play with:

use strict;
use Data::Dumper;

my @wrong = [2,1];
my @right = (2,1);
my $ref   = [2,1];

print 'right: ', Dumper \@right;
print 'right: ', Dumper $ref;
print 'wrong: ', Dumper \@wrong;
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Update: this is a common pitfall that probably all of us have stumbled on at least once ... i sure have!

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)