Uninitialized value $sOptions

We need a second test in case the second match isn't fulfilled either.
Example:
```
sub subr {
##  @baz;
}
```

Author: albert-github

lib/Doxygen/Filter/Perl.pm

@@ -827,7 +827,11 @@ sub _ProcessDoxygenCommentBlock
       # Lets check special case with a '.' or ',' e.g @winchhooks.
       $sCommandLine =~ /^\s*#\*\*\s+\@([\w:]+)([\.,].*)/;
       $sCommand = lc($1);
-      $sOptions = "$2";
+      $sOptions = "";
+      if (defined($2))
+      {
+        $sOptions = "$2";
+      }
     }
     $logger->debug("Command: $sCommand");
     $logger->debug("Options: $sOptions");