I don't quite understand the question. That code works for me (although you might want to check if open() returns an error).

Are you asking how to ask the user for a file name? You could use Perl/Tk for a dialog-based approach, or here's a unrefined console-based approach:

print("Enter local filename, or just Enter to abort: ");
my $local_filename = <STDIN>;
chomp($local_filename);
if ($local_filename ne '')
{
   open
   ...
}
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