Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Examples:

This first example causes all lines that start with -INC (and possibly preceding blanks) to be treated as include directives:

  pp( include( 'id(-inc)'))

This second example causes all lines that start with ++INCLUDE (and possibly preceding blanks) to be treated as include directives:

  pp( include( 'id(++include)'))
Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide