The nmake program and inheritance of environment variables and variables (macros) of make-files

Question

Could you please tell me what is the reason for such different behavior when inheriting variables (macros)?

Example #1 (the simplest one).
The contents of the makefile "calling.mak":

# variable inheritance checking

TEST_VARIABLE1 = 30

!IF [set TEST_VARIABLE1=30]
!ENDIF

!IF [$(MAKE) /l /e /f called.mak task1]
!ENDIF

!MESSAGE
!MESSAGE *****
!MESSAGE value TEST_VARIABLE1 on calling makefile is -- $(TEST_VARIABLE1) --
!MESSAGE env-var TEST_VARIABLE1 output by the command `set TEST_VARIABLE1` in calling makefile:
!IF [set TEST_VARIABLE1]
!ENDIF
!MESSAGE value TEST_VARIABLE2 on calling makefile is -- $(TEST_VARIABLE2) --
!MESSAGE env-var TEST_VARIABLE2 output by the command `set TEST_VARIABLE2` in calling makefile:
!IF [set TEST_VARIABLE2]
!ENDIF
# Which is kind of understandable.
# The nmake.exe program inherits those environment variables that were defined before it was called.
!MESSAGE *****
!MESSAGE

The contents of the makefile "callied.mak":

# variable inheritance checking

TEST_VARIABLE1 = 40

task1 : task2
    @ echo:
    @ echo( #####
    @ echo value TEST_VARIABLE1 in task1 on called makefile -- $(TEST_VARIABLE1) --
    @ echo env-var TEST_VARIABLE1 in task1 on called makefile -- %%TEST_VARIABLE1%% --
    @ echo env-var TEST_VARIABLE1 output by `set TEST_VARIABLE1` in task1
    @ set TEST_VARIABLE1
# Setup env-var TEST_VERIABLE2 from TEST_VARIABLE1
    @ set TEST_VARIABLE2=%%TEST_VARIABLE1%%
    @ echo value TEST_VARIABLE2 in task1 on called makefile -- $(TEST_VARIABLE2) --
    @ echo env-var TEST_VARIABLE2 in task1 on called -- %%TEST_VARIABLE2%% --
    @ echo env-var TEST_VARIABLE2 output by `set TEST_VARIABLE2` in task1
    @ set TEST_VARIABLE2
    @ echo:
    @ echo( #####

task2 :
    @ echo:
    @ echo( #####
    @ echo value TEST_VARIABLE1 in task2 on called makefile -- $(TEST_VARIABLE1) --
    @ echo env-var TEST_VARIABLE1 in task2 on called makefile -- %%TEST_VARIABLE1%% --
    @ echo env-var TEST_VARIABLE1 output by `set TEST_VARIABLE1` in task2
    @ set TEST_VARIABLE1
    @ echo value TEST_VARIABLE2 in task2 on called makefile -- $(TEST_VARIABLE2) --
#   @ echo env-var TEST_VARIABLE2 in task2 on called -- %%TEST_VARIABLE2%%  --
#   @ echo env-var TEST_VARIABLE2 output by `set TEST_VARIABLE2` in task2
#   @ set TEST_VARIABLE2
# If you uncomment the lines above, it will fail. Which is kind of understandable.
# Target "task1" will be executed after target "task2" is processed.
    @ echo:
    @ echo( #####

Let's set the environment variable TEST_VARIABLE1:
set "TEST_VARIABLE1=10"
Let's check its value:
set TEST_VARIABLE1

TEST_VARIABLE1=10

Now run the nmake.exe program with this command:
nmake.exe /elf calling.mak
Otputs:

#####
value TEST_VARIABLE1 in task2 on called makefile -- 30 --
env-var TEST_VARIABLE1 in task2 on called makefile -- 30 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task2
TEST_VARIABLE1=30
value TEST_VARIABLE2 in task2 on called makefile -- --
#####

#####
value TEST_VARIABLE1 in task1 on called makefile -- 30 --
env-var TEST_VARIABLE1 in task1 on called makefile -- 30 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task1
TEST_VARIABLE1=30
value TEST_VARIABLE2 in task1 on called makefile -- --
env-var TEST_VARIABLE2 in task1 on called -- 30 --
env-var TEST_VARIABLE2 output by set TEST_VARIABLE2 in task1
TEST_VARIABLE2=30
#####

*****
value TEST_VARIABLE1 on calling makefile is -- 10 --
env-var TEST_VARIABLE1 output by the command set TEST_VARIABLE1 in calling make file:
TEST_VARIABLE1=30
value TEST_VARIABLE2 on calling makefile is -- --
env-var TEST_VARIABLE2 output by the command set TEST_VARIABLE2 in calling make file:
Environment variable TEST_VARIABLE2 not defined
*****

Now let's change the line in the make-file from this one !IF [set TEST_VARIABLE1=30] to this one !IF [set "TEST_VARIABLE1=30"]
Run the nmake.exe program with this command:
nmake.exe /elf calling.mak
Otputs:

#####
value TEST_VARIABLE1 in task2 on called makefile -- 10 --
env-var TEST_VARIABLE1 in task2 on called makefile -- 10 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task2
TEST_VARIABLE1=10
value TEST_VARIABLE2 in task2 on called makefile -- --
#####

#####
value TEST_VARIABLE1 in task1 on called makefile -- 10 --
env-var TEST_VARIABLE1 in task1 on called makefile -- 10 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task1
TEST_VARIABLE1=10
value TEST_VARIABLE2 in task1 on called makefile -- --
env-var TEST_VARIABLE2 in task1 on called -- 10 --
env-var TEST_VARIABLE2 output by set TEST_VARIABLE2 in task1
TEST_VARIABLE2=10
#####

*****
value TEST_VARIABLE1 on calling makefile is -- 10 --
env-var TEST_VARIABLE1 output by the command set TEST_VARIABLE1 in calling make file:
TEST_VARIABLE1=10
value TEST_VARIABLE2 on calling makefile is -- --
env-var TEST_VARIABLE2 output by the command set TEST_VARIABLE2 in calling make file:
Environment variable TEST_VARIABLE2 not defined
*****

Now let's change the line in the make-file from this one !IF [set TEST_VARIABLE1=30] to this one !IF [set TEST_VARIABLE1=30 & set TEST_VARIABLE3=70]. And add lines to the "calling.mak" and "called.mak" files to check the result.
nmake.exe /elf calling.mak
Otputs:

#####
value TEST_VARIABLE1 in task2 on called makefile -- 30
env-var TEST_VARIABLE1 in task2 on called makefile -- 30
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task2
TEST_VARIABLE1=30 & set TEST_VARIABLE3=70
value TEST_VARIABLE2 in task2 on called makefile -- --
value TEST_VARIABLE3 in task2 on called makefile -- --
env-var TEST_VARIABLE3 in task2 on called -- %TEST_VARIABLE3% --
env-var TEST_VARIABLE3 output by set TEST_VARIABLE3 in task2
Environment variable TEST_VARIABLE3 not defined
NMAKE : fatal error U1077: 'set' : return code '0x1'
Stop.

*****
value TEST_VARIABLE1 on calling makefile is -- 10 --
env-var TEST_VARIABLE1 output by the command set TEST_VARIABLE1 in calling make file:
TEST_VARIABLE1=30 & set TEST_VARIABLE3=70
value TEST_VARIABLE1 on calling makefile is -- --
env-var TEST_VARIABLE2 output by the command set TEST_VARIABLE2 in calling make file:
Environment variable TEST_VARIABLE2 not defined
value TEST_VARIABLE3 on calling makefile is -- --
env-var TEST_VARIABLE3 output by the command set TEST_VARIABLE3 in calling make file:
Environment variable TEST_VARIABLE3 not defined
*****

Now let's change the line in the make-file from this one !IF [set TEST_VARIABLE1=30] to this one !IF [set TEST_VARIABLE1=30] && [set TEST_VARIABLE3=70].
nmake.exe /elf calling.mak
Otputs:

#####
value TEST_VARIABLE1 in task2 on called makefile -- 30 --
env-var TEST_VARIABLE1 in task2 on called makefile -- 30 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task2
TEST_VARIABLE1=30
value TEST_VARIABLE2 in task2 on called makefile -- --
value TEST_VARIABLE3 in task2 on called makefile -- 70 --
env-var TEST_VARIABLE3 in task2 on called -- 70 --
env-var TEST_VARIABLE3 output by set TEST_VARIABLE3 in task2
TEST_VARIABLE3=70
#####

#####
value TEST_VARIABLE1 in task1 on called makefile -- 30 --
env-var TEST_VARIABLE1 in task1 on called makefile -- 30 --
env-var TEST_VARIABLE1 output by set TEST_VARIABLE1 in task1
TEST_VARIABLE1=30
value TEST_VARIABLE2 in task1 on called makefile -- --
env-var TEST_VARIABLE2 in task1 on called -- 30 --
env-var TEST_VARIABLE2 output by set TEST_VARIABLE2 in task1
TEST_VARIABLE2=30
value TEST_VARIABLE3 in task1 on called makefile -- 70 --
env-var TEST_VARIABLE3 in task1 on called -- 70 --
env-var TEST_VARIABLE3 output by set TEST_VARIABLE3 in task1
TEST_VARIABLE3=70
#####

*****
value TEST_VARIABLE1 on calling makefile is -- 10 --
env-var TEST_VARIABLE1 output by the command set TEST_VARIABLE1 in calling make file:
TEST_VARIABLE1=30
value TEST_VARIABLE2 on calling makefile is -- --
env-var TEST_VARIABLE2 output by the command set TEST_VARIABLE2 in calling make file:
Environment variable TEST_VARIABLE2 not defined
value TEST_VARIABLE3 on calling makefile is -- --
env-var TEST_VARIABLE3 output by the command set TEST_VARIABLE3 in calling make file:
TEST_VARIABLE3=70
*****

What is the reason for this behavior? How can I ensure that nmake inherits variables and macros normally? Actually, it is required to transfer macros from one makefile to another when they are connected via a directive !INCLUDE in the third makefile. Previously, as I remember in version 1.5, there was such a wonderful command line key as "/V". But, apparently, he got lost somewhere along the way.