[Groff] Question on TBL

[Michael Hobgood]

A question about tbl:
While marking up chapter four of the UTP
I entered this table:

.TS
center box tab (#);
cfCWw (.5i) | cfCWw (2.5i) | cfIw (.5i).
po#ll#right
\^#\^#margin
.TE

When formatting it, tbl gives the error
message:
        unrecognized format `('
        giving up on this table

However, if I change the last column entry
and make the table look like this:

.TS
center box tab (#);
cfCWw (.5i) | cfCWw (2.5i) | cw (.5i)fI.
po#ll#right
\^#\^#margin
.TE

then tbl will process the table correctly.

Why do I need to change the order of the modifers
on the format line for the last column for this
to work?

Michael Hobgood