qr {
    ^                           # Anchor at the start
    _?                          # Optional underscore
    [\#*]*                      # Optional sharps and stars
                                # Numerical part:
      [0-9]+                    #   Digits
      (?:                       #   Optional
        \[\s*[0-9]+-[0-9]\]     #    '[', whitespace, digits, '-', digit, ']'
      )?                        #   End optional
    [\#*]*                      # Optional sharps and stars
                                # Character part:
      X*                        #   Zero or more 'X'
      (?:                       #   Optional
                                #     Either
        !X*                     #       '!' followed by 'X's,
           (?:\.X*)?            #       optionally '.' followed by 'X's
        |                       #     or
        \.X*                    #       '.' followed by 'X's,
           (?:!X*)?             #       optionally '!' followed by 'X's
      )?                        #   End optional
    $                           # Anchor at the end.
}x;