use % for positive integer values.
What does make you think that the use % of is limited to positive integers? 
$ perl -le 'print for map $_%-3, -18..-15'
0
-2
-1
0

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In reply to Re^2: Find if a number is a multiple of a number. by blazar
in thread Find if a number is a multiple of a number. by Baratski

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