Actually, it's your own script, not File::Copy, that causes the script to die:

        copy($localfile, $installfile)
            or die "unable to copy to $installfile\n";
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If you were to drop the "or die..." part, it wouldn't do that. It wouldn't replace the file that was there, either, so it's not the best of solutions.

$installfile looks like it contains an absolute path to me. You may try to delete a file without checking if it did indeed exist, like this:

        unlink $installfile;
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No error checking here: if it fails, nothing happens. If you were to put this line just in front of the line containing the copy(), including the die() part, this would likely do the proper thing: replace an existing file, and die() if it fails.