If you use /^(?:"([^"]+)"|(-))$/, the matching expression is not always in the same variable, but it is always in $1 || $2 :)

Eh, no. Consider:

"0" =~ /^(?:"([^"]+)"|(-))$/;
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Then $1 || $2 is actually undefined (because $1 is 0, hence false, and $2 is undefined). If the OP uses 5.10 or later, he could use $1 // $2, but then there's a better solution available as well (see my other post).