You probably want to do something like

Notice that the single quotes were replaces by backticks. There are certain problems with using backticks, but it's usually OK to use them to run a simple and safe command.

Also, your current code will only capture v09.11. If you want to capture v09.11-e020, use this:

my ($exp) = $var =~ m/(v\d{2}\.\d{2}-[a-z]\d{3})/;
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