In my example INCLUDE='one;two' is an environment variable, and the file is included as include 'blah.inc'. Fasm can handle several paths only when they are provided in an environment variable, not after include keyword.
I see that you are using an absolute path /sys/lang.inc, i.e. you are trying to compile from KolibriOS. Well, KolibriOS doesn't support environment variables. If your aim is to be able to compile your program from both KolibriOS and Windows/Linux, then you can do as follows:
Copy all the standard includes (like macros.inc and lang.inc) to the directory of the main *.asm file of your program.
Include these standard includes without specifying any path, just include 'macros.inc'.
Compile from KolibriOS as usual.
Compile from Windows/Linux specifying INCLUDE environment variable with paths to standard includes.
match =NOTHING,AUTOBUILD {
include ''/sys/lang.inc'
include ''/sys/macros.inc'
}
match =YES, AUTOBUILD {
include 'lang.inc'
include '../../../macros.inc'
}