Three questions in one post? Sheesh...
You can also split a word into characters, sentence into words, and paragraph into sentences:
$info = "This:is:splitting:me:up:inside";
@personal = split(/:/, $info);
@chars = split(//, $word);
@words = split(/ /, $sentence);
@sentences = split(/\./, $paragraph);
2) Use some of these:
$string =~ s/[^a-zA-Z0-9]//g; #^ means all things NOT in this range
$string =~ s/\W//g; #anything not alphanumeric
$string =~ s/[^\w ]//g; #alphanumeric with spaces
3) It'd be a bit more complex and ugly than PERL needs to be, and it wouldn't be as efficient, but you could use various tricks like looking for query strings or form field values in order to display certain information...Of course, sessions and cookies could make this easier on you...and of course, PHP would make it much easier, but it can be done in PERL.