Two minor escaping issues using \preformatted{....} in Rd format

Hi r-devels,

I have two minor problems with special characters in Rd files when
used within a  \preformatted{} markup command:

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1. issue: backslash + single brace
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I would like to write "\\\}" to produce \} on output (documenting
the need to escape the brace once again before TeX-ing it);
this fails if there is no space between the second and third
backslash, but works if there is a space, but this produces
\ } then....

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2. issue: backslash + percent sign
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I would like to write "\\\\\%" to give a string argument \\% on
output; this is needed for documenting how to register special
operators to TeX package 'listings'.
Again this fails, while "\\\\ \%" works.

In neither case 1 or 2 the standard TeX trick to produce a
linebreak in the source without producing a space on output
helps, i.e.

\\%
\}

resp.
\\\\%
\%

both produce valid code [the resp. first % is read as a comment
sign] but also insert a non-intended space in the output.

Any idea how to circumvent this?
Best, Peter