; -- returns next available index in return data array
VALNUM(ERR,X,DOM)
; return error if invalid number
LKSCRN(ORLST,FROM,DIR,REF,GBL,SCR)
; Return a set of entries from xref in REF
; .Y=returned list, FROM=text to $O from, DIR=$O direction,
; REF=subscript indirection global ref including xref,
; GBL=standard FM global ref, SCR=reference to screen in 101.41