This is true enough in non-dynamic languages such as C. If I recall, Ruby and Python support the arbitrary code bit in their own fashion, so this isn't a point strictly in favour of Perl.
My criteria for good software:
Does it work?
Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
I personally believe that (oh... well... then) it won't be strictly a point in favour of Perl, but it will still be slightly so due to the fact that "their" arebitrary code won't be just as sexy as ours! :)