in reply to PAR::Packer exclude modules - but which ones?

You could make a packed .pl that relies on the target machine having a perl interpreter and core modules:
pp -P -o out.pl script.pl
Then unzip it:
unzip -l out.pl | sort -n
I tried it on a 370 byte script, and the result was a packed .pl that was 272 bytes, smaller than the original. Cool!