Rtrim$ returns a copy of the string StrExpr in which the right
blanks have been trimmed, trailing spaces removed. If StrExpr consists
entirely of blanks, rtrim$ returns the empty string.
EXAMPLE
The program
a$ = " Please, Honey, I need my space! "
b$ = rtrim$(a$)
print ">" a$ "<"
print ">" b$ "<"
produces
> Please, Honey, I need my space! <
> Please, Honey, I need my space!<