how to print a traceback?

[sndive at gmail.com]

i'm struggling to get some proxy code working with liburl[2] and want
to print
some tracebacks in my class ProxyHTTPConnection::request().
do i have to force an exception and print a backtrace in catch or
can i just print the current stack?
print_tb takes an argument and short of forcing an exception
i don;t know where to get the current backtrace object from.

thanks.