installing a known tar.gz

[ara.t.howard]

hi all-

i'm trying to compile the latest ruby (stable-snapshot.tar.gz) using  
the ports compiler toolchain.  i though i might be able to do  
something like

   sudo cp stable-snapshot.tar.gz distfiles/ruby/ruby-1.8.6.tar.gz
   sudo port -p -f install ruby

but no joy.  that complained about the checksums.  next i edited the  
Portfile to reflect that actual checksums but still no joy.

is there a preferred mechanism for doing what i'm trying to do:  
install a port with an alternate tarball?

sorry for the barrage of newbie questions - the switch from linux is  
going a bit slower that i'd hoped.  lot's of new things to learn.

kind regards.

a @ http://codeforpeople.com/
--
we can deny everything, except that we have the possibility of being  
better. simply reflect on that.
h.h. the 14th dalai lama