> It also erroneously replaces things like '$prefixpath'. It should probably do split the path on the path separators and only replace components that are equal to $prefix or $exec_prefix (so that the '$' can be escaped for directories named as such literally, but that would require a pass to parse the escapes).

re.sub() can be used to leave $prefixpath unchanged. Yeah, please open a separed issue. Sorry, I missed this part of the bug report.