Hey if you only want alphanumeric, here you are :

open FILE, "something";
while (<FILE>) {
  s/[^A-Za-z0-9!?,.;:'"]//g;
  print $_;
}
[download]

Add whatever charakter you want to see to the !?,.;:'" part.
What does this do ?
replace every charakter that is not one of the chars in [] with nothing. This might be better than list every not-wanted char in the []. the ^ at the beginning do the '!=' job :-).

Hope this will help.

-----------------------------------
--the good, the bad and the physi--
-----------------------------------
[download]