Don't prompt when you can pass arguments :)

#!/usr/bin/perl --
use strict;
use warnings;
...
Main( @ARGV );
exit( 0 );
sub Main {
    if( not @_ ){
        print "Usage: $0 filenameToOpen\n\n";
    }
    ...
}
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Read Behind the GUI lives the Shell, perlintro, perlrun, @ARGV