[Groff] [Groff & Heirloom] tbl problem with backslashes

[Blake McBride]

I found that Groff and Heirloom handle backslashes in tables differently.
 I actually think both are wrong, but I am not sure.  My input is as
follows:

.TS
a a .
INPUT PRODUCES
\\\\ \\
abc def
.TE



I am processing it with tbl & troff but no macro packages.  They produce
different results - both unexpected by me.  What I am trying to produce is
as follows:

INPUT    PRODUCES
\\       \
abc      def


(Yes, I am using tabs between the columns on the real input file.)

Thanks.

Blake