perl is smart enough that multiple use statements will not result in the warning you describe - each package will be compiled and each namespace will be populated only once. This includes cases with circular dependency, though resolving that is likely worth your time. My guess is that at some point during a refactor, the programmer forgot to delete the old version of the subroutine in the original module. Something which is the structural equivalent of

#!/usr/bin/perl
use strict;
use warnings;

use Scalar::Util qw(looks_like_number);

sub looks_like_number($) {
    1;
}
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It may be innocuous, but chances are good that the subroutines are not identical. A simple file search for sub someSubNameHere will likely show you all occurrences and lead you to the appropriate solution.