$2 in the awk script probably gets substituted with something unexpected when you evaluate it in backticks in Perl. $2 in Perl is the result of the second set of parentheses in the latest regular expression match; presumably it's empty, so the awk script is just "print".

Quote the variable properly, and it should work.

Note, though, that you have a Useless Use of Grep when you pipe to awk -- awk can grep just fine. And by the same logic, I guess it's a Useless Use of Awk to call awk from Perl, because Perl can do everything awk can, only better.

The /s option causes .* to match across newlines, so you can handle the multiple lines of output from free as one expression.