[proposal] for RPN modifications

[Angus]

NO, I was not aware of that yesterday, thank you! Althogh now that you mentioned it I remember I did know it after reading the manual last year - shame on me. Well x<->y would have striked my eye more than the arrows on the key :-)
What would be better thogh, if I could swap from the command line. I guess hp have serious problems with the implementation which makes it impossible to change that afterwords.