>>>Beauty!!
>>
>>Actually not mine, I stole that from UT or a related person :). Can't remember where I first saw it, maybe in the days when I worked with Steven Black (first or second time? hmmm). Took me some time to understand what it does and how.
>
>Did not bother yet to figure it out myself, but it worx like a charm
>so it might remain little mystery to lazies like me..

Once you get it it's easy... The inner chrtran removes the regular characters from the string leaving only unwanted ones, then the outer chrtran uses that as a list of characters to remove.