Wow, nice find, thanks for that. I'm pretty sure that setting the limit to 4 in the first case saves some cpu cycles, but setting it to 0 in the second case is pretty crazy, given the special behavior of split() in this case.

Here's one more: What's the difference between

( $a, $b, $c )           = split /:/, $str;
[download]

and

( $a, $b, $c, @options ) = split /:/, $str;
[download]

when $str = "foo:bar:"?

Spoiler: Adding @options to the left hand side makes $c undef'd!