If people here start about code layout, indentation, and useless constructs, I'd like to throw in one of my pet peeves here.

if (expression) {
    die "reason";
    }
else {
    ...
    }
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is so unnessasary cluttering. A program flow stops after a die. There is no use for an else. Same after a return is a sub

lc $first_number eq "q" and die "Goodbye\n";

... rest of code
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Is so much easier to read and maintain. For those that like statement modifiers (I don't), you can also use

die "Goodbye\n" if lc $first_number eq "q";
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