[Common Lisp considered a dumpster.]
Since Alex responded, it's not worth adding more, but still, some of Dmitry Non's points do appear in plain text in Steele's book.
For example, that prog' came first and later it was decomposed into block', let', and tagbody'.
By the way, I had a need for progv' once and I was writing something simpler than an interpreter.<br/>Maybe it was a macro (so a nanocompiler, then).<br/>I find prog1' handy often; `prog2', maybe once.