RE: rx.el sexp regexp syntax

[Drew Adams]

> For such regexps, the exact syntax (PCRE, BRE, ERE, RX, ...) in use has
> fairly little importance: if written "raw" as above, it will be
> indecipherable in any case.
> 
> To make it readable, you need to add human-level explanations
> e.g. by adding comments and naming sub-elements.  Which is indeed what
> is done in the source code:...

Agreed.