Since it's meant for 5.8.0, I didn't yet see this "real" solution for number 4:

%::=//
[download]

For later perls it's a bit longer (too long):

%::=0;//
[download]

update oops, posted under the wrong node. This is meant for node How's your Perl?

20050703 Edit by ysth: moved from How's your Perl? (II).