We are humans. Being humans, we don’t care how the numbers representing characters compare to each other. We care about the properties of characters. We should just strip out `[[:cntrl:]]` and leave it at that, like we do in other places.

(I don’t see a good reason to strip out spaces, or to start trying to decide which punctuation characters are okay. And a blacklist seems better than a whitelist because Unicode gets extended.)

For the curious, the Venn diagram of `cntrl`, `blank`, `space`, `print`, `graph` looks like this under [`use feature 'unicode_strings'`](http://perldoc.perl.org/perlunicode.html#The-%22Unicode-Bug%22):
```
!cntrl !blank !space !print !graph: "\x{378}\x{379}\x{37f}\x{380}\x{381}\x{382}…"
!cntrl !blank !space  print  graph: "!\"#\$%&'()*+,-./0123456789:;<=>?\@ABCDEFG…"
!cntrl !blank  space !print !graph: "\x{2028}\x{2029}"
!cntrl  blank  space  print !graph: " \x{a0}\x{1680}\x{180e}\x{2000}\x{2001}\x{2002}\x{2003}\x{2004}\x{2005}\x{2006}\x{2007}\x{2008}\x{2009}\x{200a}\x{202f}\x{205f}\x{3000}"
 cntrl !blank !space !print !graph: "\0\1\2\3\4\5\6\a\b\16\17\20\21\22\23\24\25\26\27\30\31\32\e\34\35\36\37\177\200\201\202\203\204\206\207\210\211\212\213\214\215\216\217\220\221\222\223\224\225\226\227\230\231\232\233\234\235\236\237"
 cntrl !blank  space !print !graph: "\n\13\f\r\205"
 cntrl  blank  space !print !graph: "\t"
```