/ELSEIF, and /ELSE are not valid outside an /IF group.
An /IF group can contain at most one /ELSE directive. An /ELSEIF directive
cannot follow an /ELSE directive.
/ENDIF is not valid outside an /IF, /ELSEIF or /ELSE group.
Every /IF must be matched by a subsequent /ENDIF.
All the directives associated with any one /IF group must be in the same
source file. It is not valid to have /IF in one file and the matching /ENDIF
in another, even if the second file is in a nested /COPY. However, a complete
/IF group can be in a nested /COPY.