in reply to Reading progress of "copy" executed asynchronously

Probably a totally useless guess: See File::Tee and IPC::Run. Sorry for typos - written on my iPad in a hurry 😎

Regards, Karl

«The Crux of the Biscuit is the Apostrophe»

perl -MCrypt::CBC -E 'say Crypt::CBC->new(-key=>'kgb',-cipher=>"Blowfish")->decrypt_hex($ENV{KARL});'Help