It's hard to decipher exactly what you want to do. It's easy to say that should always give $this_user eq 'robot'; because, if $this_user must be 0, 1, or 2, then it will never be less than 0. Try doing it by subscripting a list:

$this_user = qw( male female robot )[$this_user];
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Rearrange to taste.

-sauoq
"My two cents aren't worth a dime.";