I need some great hacks to generate a YYMMDD string as part of a backup
filename, and to get rid of old backups. This is the best I could come
up with for the former. I would welcome better ideas, or suggestions on
improving what I am doing or how I am doing it. I do like that it is
short and uncluttered by anything extraneous. I also think that it is
not intuitively obvious to the most casual user, or anyone else.

:file
backup=c![rht("0!hpyear",2)]![rht("0!hpmonth",2)]![rht("0!hpdate",2)]
.backup
:listeq

 FILE EQUATIONS

 FILE BACKUP=C970722.BACKUP

For getting rid of the old stuff:
:listf @.backup.project,6>list2del
:input oldest<list2del
:showvar oldest
OLDEST = C970711.BACKUP.PROJECT
:purge !oldest