use File::Basename qw(dirname);
my $script_dir = dirname($0);
my $path = "$script_dir/Pandoras Box/$file.txt";
...

##</code><code>##

chomp(my $file =uc(<STDIN>));
my $path = "./Pandoras Box/$file.txt";
open FILE, '>>', $path or die "unable to append to $path: $!";
...

##</code><code>##

my $path = "Pandoras Box/$file.txt";
...