This is a small function that removes the punctuation from a given string in Greek. I haven't added upper case letters or multitone letters (except one letter to show how it can be expanded to fit your needs).
This function is pretty useful when using uppercase functions in our templates, because having upper case letters with tones isn't pretty.
Besides that you can map any set of characters or strings with a given character/string and then use it to alter all the mapped elements with the given one.