The problem is that the $1, $2, etc. variables only get set if the regular expression matches. /(\d+)/ does NOT match "Mm", so no assignment occurs. What you need to do is to check whether there is a match before using the positional variables, like this: 
if ($sss =~ /(\d+)/) {
  # use $1 as you wish
}
else {
  # don't!
}

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Interestingly, your last code snippet will do the right thing if you remove the part after the && (and an extra opening parenthesis you seem to have there), because $1 and $2 will only be used when there is a match, and in that case they will contain either the strings they matched, or undef if their respective subexpressions didn't match anything.

--ZZamboni

In reply to Re: Regular Expression Question by ZZamboni
in thread What happens with empty $1 in regular expressions? (was: Regular Expression Question) by marcblecher

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