"P" is sometimes used when it's important that the thing is written in Perl (e.g.
PDL - because you can use Perl in PDL). Normally, though, you would use no prefix at all. In fact, a user will be running a program without needing to know what language it was programmed in.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]