assuming you've read your file in and assigned it to the
variable 'foo'...
rereplace(foo, '<hr />.*$', '', 'all')
should remove the first <hr /> and everything that
follows, leaving just the first log entry.
caveat: i'm n00bish with regex, so if there are any issues or
potential issues that any regex folk can see with that, please feel
free to point out 🙂