Let's assume that string T$ contains the following: "A $B".
The following does not work: a$ = word$(T$,1,"$")
But the following does work: a$ = word$(T$,1,"\\$")
Maybe there should be something in the manual to explain that dollar signs cannot be in a string unless preceded by "\\".
Or maybe there should be a complete list of characters that require special attention when placing in strings.
The problem is not special to dollar signs, but to any significant character in the regular expression syntax. Which is mentioned in the manual. But I agree it could be a little clearer that it is quite complex, or how to avoid it by using only commands that do not use regular expression syntax...