before becoming variable names. Invalid characters are replaced by
letter @samp{V} in the first position, or by @samp{_} in subsequent
positions. If the name thus generated is not unique, then numeric
extensions are added, starting with 1, until a unique name is found or
there are no remaining possibilities. If the latter occurs then the
before becoming variable names. Invalid characters are replaced by
letter @samp{V} in the first position, or by @samp{_} in subsequent
positions. If the name thus generated is not unique, then numeric
extensions are added, starting with 1, until a unique name is found or
there are no remaining possibilities. If the latter occurs then the