my $rx = qr/
             ^            # At the beginning of the string  
             (            # Capture in $1
               (?:        # Paren for grouping (don't capture in $2)
                 \w       # match a "wordy" character
                 (?:      # paren for grouping,
                   \s+|\z # match at least one space or the end of the string
                 )
               )*         # zero or more times
              )           # end of capture $1
            (.*)          # and match what comes after storing it in $2
          /x              # allow these comments
;