Suffix Wildcard?

[Drew Hubl]

Hello,

I've read up on the wildcard '%' character, and it seems as though it only
matches non-empty strings, which works great for rules like:

%.o:%.c
    $(CC) $* -o $@

but what I would like to do is match suffixes for targets, like:

tb%:
    vlog -nologo -work work tb$*.v

Where the possible target matches would be "tb", "tb_something",
"tb_something_entirely_different".

Whenever I use the above rule with a nonzero suffix (like "tb_something"),
the command that gets run is as expected:
vlog -nologo -work work tb_something.v

Whenever I try to make the plain "tb" target, the command that gets run is
a bit unexpected:
vlog -nologo -work work tb.o.v

When what I expected was:
vlog -nologo -work work tb.v

Is there a similar wildcard character that also matches empty strings, or
can I turn off automatically inserting ".o" in place of the '%'?

Thanks.
-- Drew