bmake variable expansion: ${X:ts:}

[Brook Milligan]

I am trying to understand the use of :ts as a bmake variable expansion 
modifier.  No doubt I am doing something wrong, but I cannot figure this out.

Below is a small Makefile.  Its intent is for the loops to have three 
iterations (a, b, and c) by separating ${X} on the colons.

When I run this, however, there is only one iteration (for a:b:c).

Any help is appreciated.

Thanks.

Cheers,
Brook


# Makefile

X=      a:b:c

all:
        @echo "X=${X}"
        @echo "make .for loop:"
.for f in ${X:ts:}
        @echo "===> ${f}"
.endfor
        @echo "shell for loop:"
        for f in ${X:ts:}; do echo "===> $${f}"; done