Read how URL rewriting works.
Allows manipulating download pages into proper download URLs. If information required to generate the URL is not present, the site needs urlrewriting plugin.
Example
urlrewrite:
sitename:
regexp: 'http://imaginary.org/tor/(?P<id>\d+)/(?P<name>.*)'
format: 'http://imaginary.org/download/\g<id>/\g<name>'
This would rewrite URL
http://imaginary.org/tor/1234/test.torrent
to:
http://imaginary.org/download/1234/test.torrent
Few regexp characters absolutely need to be escaped with \ (in context of urls). At least + and ? metacharacters.
Example
http://example.com/?id=1234
should be
http://example.com/\?id=(?P<id>\d+)