"av and alf are useful globals used in e.g. gradeup and vars.
"from ''the apl handbook of techniques'' copyright 1978, ibm.
av#' abcdefghijklmnopqrstuvwxyz'
alf#av,'H`_`a`b`d`e`f`g`h`i`j`k`l`m`n`o`p`q`r`s`t`u`v`w`x`y`z?0123456789'