Programming :: Difficulties Running Commands In Shells From Perl?

I'm getting something(s) wrong, trying to run commands (both simple and piped) in shells from Perl programs. The ultimate objective is to set up "copy X selection to clipboard" from urxvt but apparently simple debugging statements are not working.Here's the Perl, taken from here and modified to use xclip instead of xsel and with debugging added, shown in green

Code:
#! /usr/bin/perl
sub on_sel_grab {

[code]....