When you do your return, you should not return an empty string. It works as long as you return it as just a string which gets check but lets suppose this,

my @result = $object->cleanup;

if (@result) {
  print "Got some results back '@result'\n"
}
__END__
#
# You will always get this back if you do return '';
#
Got some results back ''
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You always return undef for nothing and your code will work in the way you think and it is easier to read. Just replace that last bit with this.

  return $_[0];
}
return;
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