I only remember this vaguely, but a while back I had a co worker ask me to write a simple parser to parse a proxy-cache log entry, sort of similar to Apache logs... where entries could be:

• all alpha-numeric characters w/o any whitespace
• double-quoted alpha-numeric characters ( whitespaces allowed ) where a double-quote is escaped with another double-quote

He encountered problems because he was trying to separate out the fields using split. Obviously, since an entry can contain spaces if it's quoted, you couldn't really split()

So the approach I took was something like this:

    # untested... I'm sure this doesn't really work...
    while( $line =~ m{\G\s*(\[\w0-9]+|"(?:[\w0-9]|"")+")}g ) {
        do_something_with_match($1);
    }
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something like that. come to think of it, it's probably not a good example... oh well. my $0.02