Wildcard error messsage (was Re: Ignorant XY4 question)

[Eric Van Tassel 101233.342@xxxxxxxx]

I've been (idly and inattentively) lurking on this thread, thinking I
should be following more closely because I too have had some disappointing
error messages on wildcard global changes.

But today I read the following:

>... the following is perfectly legal ...
>
>CI /19{WN}{WN}/20{WN}{WN}/
>
>This, and quite logically, will generate the error message for sure:
>
>CI /19{WN}{WN}/{WN}{WN}20/
>
>This ought not to cause problems, but will, after making one
>replacement, stopping at that point, and whimpering:
>
>CI /19{WN}{WN}/20{WN}{WN}/

I've just opened a spare file with a bunch of 18th-century dates in it, and
commanded
  CIA |17{WN}{WN}|{WN}{WN}18|
XyWin made 108 changes -- correctly, so far as a quick browse through the
file reveals.

Then I ABandoned the file, reopened it, and commanded
  CIA |17{WN}{WN}|18{WN}{WN}|
Again, XyWin made 108 changes all of which seem to be kosher.

What am I doing right (so to speak)?

I'm afraid I deleted R.v.R.'s previous message, but I believe he mentioned
the "wx" wildcard function. The "for sure" error-message-generator and my
own test version both use {WN}, not {WX} -- is that the difference?

Cheers
Eric Van Tassel