Dear Richard,

> Following the ANSI standard might be a good idea.  It rules that | is just
> like +; you may have |, ||, |+, |>, and a whole bunch of things, but
> |[ |( )| ]| are no more problematic than +[ +( )+ or ]+.
> 
> || _is_ a single token according to ANSI rules, so when you would have
> accepted "| |" you just have to tweak the parser to accept "||" as well.
> 

Muchissimas gracias, sennor!

Guillermo