Untitled

Makefile:
#########
TEST_DEFAULT+= A B C

TEST= ${TEST_DEFAULT} 1

DEBUG+=TEST: ${TEST}
.for S in ${TEST}
S2=${S}
S3=${S}
DEBUG+=XXX
DEBUG+=S: ${S}
DEBUG+=S2: ${S2}
DEBUG+=S3: ${S3}
.endfor

all:
        @echo ${DEBUG}


makefile output:
################
nexus !! # make all
TEST: A B C 1 XXX S: A S2: 1 S3: 1 XXX S: B S2: 1 S3: 1 XXX S: C S2: 1 S3: 1 XXX S: 1 S2: 1 S3: 1

question:
#########
why S2 always = 1?