Oh, you want to recognize words. You know, you don't have to leave the ASCII realm to realize that that is more tricky than just matching letters and not matching punctuation symbols. Not matching punctuation symbols means rejecting "don't" as a word.

As for matching Unicode letters, we have:

    "ญᴥ一ךى" =~ /^\p{L}+$/

which is a sequence of (Unicode) letters, but from 5 different scripts. Do you want to match that?

And then I haven't touch the can of worms called 'combining sequences'. Many (all?) of the accented Unicode characters can also be formed by taking the base character, and adding the various decorations to them. Not to mention that most combinations of a base character and decorations don't have a Unicode code point, and will have to be made by combining sequences.