With a few small changes to avoid trashing my system, and after changing $OUN to $UID, this works for me.

Maybe it's something weird with your system or your shell?. What kind of system are you on? What is $ENV{SHELL} set to? Does system("ls |cat"); work?

Or maybe it's an invisible character (like a carriage return) in one of your strings. Try piping the program through cat -e to show any nonprinting characters.

A third idea is to strace/truss/ktrace your program, to see what it's actually running.