why exerb packed binary can be packed by UPX but
rubyscript2exe packed one cannot?
True. An executable generated by RubyScript2Exe can't be
compressed by UPX. I don't know why. But since RubyScript2Exe
(more precisely: EEE) compresses internally, you don't need to
compress it once again.
Erik V. - http://www.erikveen.dds.nl/