Where is $ERL_TOP on a macports installation of Erlang

I've installed Erlang through macports on my macbook and I'm trying to use the Erlang Eclipse plugin, but it needs me to point it to the $ERL_TOP directory.

Where does that exist? I know my erl binary shell开发者_如何学JAVA is located at:

which erl
/opt/local/bin/erl

Found a symbolic link in /opt/local/bin/to_erl that brought me to: /opt/lib/erlang

This appears to be my $ERL_TOP

Mine was slightly different: /opt/local/lib.