       10 // Identifier test program
       20 //
       30 aap:=aap+1  // Calls function to assign to variable
       40 SYS assert, aap=4  // Value from variable
       50 aap#:=2  // Different variable
       60 aap$:="Hallo allemaal"
       70 aap  // Procedure call
       80 SYS assert, aap#=3
       90 PRINT "Ok"
      100 //
      110 FUNC aap
      120   RETURN 3
      130 ENDFUNC aap
      140 //
      150 PROC aap
      160   SYS assert, aap=4
      170   SYS assert, aap#=2
      180   SYS assert, aap$="Hallo allemaal"
      190   olifant
      200 ENDPROC aap
      210 //
      220 PROC olifant CLOSED
      230   IMPORT aap#
      240   aap#:+1
      250   SYS assert, aap#=3
      260   SYS assert, aap=3  // Calls function
      270 ENDPROC olifant
