Just let me note that if you don't define the encoding of the the filehandle you're reading from (DATA here) then the strings you read in will be byte strings and then matching a unicode class such as /\p{Alnum}/ won't make much sense on them. In this case, perl will act as if the string would be iso_8859_1-encoded. (You can call this a bug or a feature.) This might not work with text of a different encoding, such as iso_8859_2. It will accidentally work with Hungarian text encoded as iso_8859_2, as the only Hungarian letters not in 8859_1 are \x{151}, \x{150}, \x{171}, \x{170} which are in positions \xf5, \xd5, \xfb, \xdb, which are letters (although different letters) in 8859_1. However, other languages use letters such as \x{15b}, which is encoded to 8859_2 as \xb6, and that's a non-alnum symbol in 8859_1. With other encodings, such as utf-8, you'll probably have even more serious failures.

If you want to match letters in non-ascii texts, you have two options. One is to set the encoding of the filehandle with either binmode, 3-arg open open the encoding pragma, the -C command line option, the PERLIO env-var, or some other way; or decode the string with the Encode module after reading. The other is to stay with byte string, set the correct locale with the environment variables (the locale has information about the character set, like what chars are alphabetic etc), use locale; to make the matching locale-aware, and match for /\w/ or /[[:alnum:]]/

Update: for peacekorea: please don't let this discussion confuse or frighten you, it's not quite important for the original goal. I'd just like to spread information about internationalization for the Americian monk who thinks naïvely thinks other languages all use 8859_1 just a handful of accented letters.