Btw, more or less off-topic, CGI::Util can unescape unicode with the uXXXX convention but does not follow this convension when doing escaping -; i.e. I changed its encoding routine from

$toencode=~s/([^a-zA-Z0-9_.~-])/uc sprintf("%%%02x",ord($1))/eg;
to

$toencode =~ s/([^a-zA-Z0-9_.-])/(ord($1) > 255) ? sprintf("%%u%04X", ord($1)) : sprintf("%%%02X", ord($1))/eg;