Because input lines 1 and 3 are only 4 spaces, no tabs can be unexpanded!
:ARGS
-t 8u
:INPUT
    XXXXXX
	XXX	XXX
    XXXXXX
:OUTPUT-FILTER
:EXPECTED
    /*******************/
    /* XXXXXX          */
    /*     XXX     XXX */
    /* XXXXXX          */
    /*******************/
:EOF