Beware the Aging Brain: Or The Perils of "Numbered Parameters"

I'm trying to write a short G-code to cut a straight edge along the west side of a block. The plan is to set G55 X=0 at the desired finished edge, back away, X<0, and then make multiple passes, increasing X by steps while "current_X" <=0.

As a first attempt I wanted to make sure I understood that I had the correct value for "current_X" in G55.

"I thought" this link means G55's X value is stored in #5241--but (DEBUG,#5241) returns instead, apparently, the OFFSET of G55 X from G53 X0.

After "about an hour", and after concluding "surely" I've done something like before, I grepped for "#5241" in all the files in my G-code archive.  There was one hit--again, surprising me.  LUCKILY for me, the line containing "#5241" was just above one referring to "#5421".  Dyslexia? Anyone else?  Indeed, "#5241" contains G55's X-OFFSET, but "#5421" G55's RELATIVE X position.

This is how we've been going, slipping down. I'm really regretting all those early beers. (I don't mean today: I mean in my youth.)

The documentation for #5241, which is what I read and where I stopped reads:
"5241-5250 - Coordinate System 2, G55 for X, Y, Z, A, B, C, U, V, W & R. Persistent. "

#5421's is a little clearer although it doesn't mention the UCSs individually:
"5420-5428 - Current relative position in the active coordinate system including all offsets and in the current program units for X, Y, Z, A, B, C, U, V & W, volatile. "

However, I would have missed that anyway because it doesn't contain the word "G55."

Incidentally, there was another brief struggle on the carpet with the misperception that I'd dyslexed the 2 and the 4 in #5241/#5421, when in fact the Careful Reader will have realized that the variable which was wanted for G55's relative X value is:
#5420,
#5421 being of course reserved for G55's relative Y value.

We're sorted now, but already fearing waking up to a different reality tomorrow.

(You ought to see me try to remember my cell number. My wife says it's a hoot.)