I doubt this part works:

if (!Exists($show_table_frame))

as the syntax is exists. You might want to use defined rather. Also, try not using our but rather define the variable outside the subroutine.

Finally, all this is overkill, where you can simply use the following:

if ($frame->ismapped) {
    $frame->packForget();
}
else {
    $frame->pack(@{$frame->{PackInfo}});
}
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