shell中关于IFS和for的奇怪现象

代码如下：

#!/bin/sh

VAL="/aaa/bbb/ccc/ddd//@PLATFORM/eee/fff"

IFS="@PLATFORM"

for var in $VAL
do
echo "$var"
done

结果如下：
~$ sh -x ./test.sh

• VAL=/aaa/bbb/ccc/ddd/@PLATFORM/eee/fff
• IFS=@PLATFORM
• for var in '$VAL'
• echo /aaa/bbb/ccc/ddd// /aaa/bbb/ccc/ddd/
• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo ''

• for var in '$VAL'

• echo /eee/fff
  /eee/fff

理论上不应该是只输出/aaa/bbb/ccc/ddd/和/eee/fff两行吗