in reply to numeric manipulation

This is one of several ways to do this, but if it is homework, you'd better hit PerlDoc and make sure you can explain how your chosen solution works:

$input = '7-12'; 
$input =~ /(\d+)-(\d+)/ and print $1 .. $2 or die 'Bad input';;
7 8 9 10 11 12

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In Section Seekers of Perl Wisdom