The $combination variable returned by the iterator is an array reference, so you need to de-reference it in order to print. The following will print each combination on a line, with each element separated by a tab character: 
print $output join("\t",@{$combination}) . "\n";

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The @{ } construct is what de-references the array reference

In reply to Re: Misprinting combinations / iterator by tangent
in thread Misprinting combinations / iterator by blacknail

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