[Groff] Attaching a string to the beginning of each line?

[Greg 'groggy' Lehey]

I'm currently thinking about how to simulate email replies in groff.
Things like:

Bob said:
> Fred said:
>> Bill opined:
>>> Foo
>> Bar
> Baz

I know about vertical position traps, but is there an easier way to
generate the > characters at the beginning of the line?  I'm thinking
of a source file which looks like this:

Bob said:
.quote +1
Fred said:
.quote +1
Bill opined:
.quote +1
Foo
.quote -1
Bar
.quote -1
Baz
.quote -1

Greg
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