This has nothing at all to do with Perl, and everything with Unix (and shells), so I keep it brief.

./Program.pl contains a slash. That means, the setting of your path is irrelevant. You ask for the program Program.pl in the current directory to be executed. Which isn't there to begin with. Either use just the name of the program you want to execute, a relative path to the executable, or an absolute path.

Abigail