Correct usage of experimenal::smartmatch warnings
There was incorrect usage of experimenal::smartmatch warnings category using only identifier smartmatch instead of experimenal::smartmatch. This leads to following error: "Unknown warnings category 'smartmatch'".
Also this feature is available since Perl v5.017011, not since 5.018 which was used before.
The code wasn't tested on Perl v5.017011 or newer. Therefore the bug wasn't discovered before.