You're doing far more work than you have to. printf has a %b format for printing numbers out in binary:

#!/usr/bin/perl -w
print "Input number: ";
my $num = <>;
my $len = (length(sprintf("%b", $num)) + 7) & ~7;
printf "\nBinary: %0${len}b\n", $num;
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--MrNobo1024
s]]HrLfbfe|EbBibmv]e|s}w}ciZx^RYhL}e^print