No. Your program does not add / signs.

It adds backslashes (\ "signs"), and this is unsurprising:

    $X =~ s/\Q$A\E/\Q$B\E/g;  # THIS IS NOT RIGHT
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On the replacement side of s///, \Q and \E apply quotemeta to the replacement string.

You want quotemeta only on the regex side of s/// to escape all regex meta characters, and usually never on the replacement side.

If you leave them out, you get the plain replacement:

    $X =~ s/\Q$A\E/$B/g;  # THIS IS NOT RIGHT
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