That's a warning, not an error ... it results from trying to convert a hex 'number' which has a newline in it. Remove the newline:

my $hex_num = '0x' . sprintf('%x', $dec_num);
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Also, don't use quotes when you copy $hex_num to $num at the end of the loop (it doesn't make a difference here, but it is a bad habit to get into).

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)