Something

$ sudo pkg_delete ruby18-postgres-0.7.1_2
Password:
Sorry, try again.
Password:
[dan@supernews:~/src/ruby-postgres] $ sudo gem install ruby-postgres
Need to update 1 gems from http://gems.rubyforge.org
.
complete
Select which gem to install for your platform (amd64-freebsd6)
 1. ruby-postgres 0.7.1.2006.04.06 (ruby)
 2. ruby-postgres 0.7.1.2006.04.06 (mswin32)
 3. ruby-postgres 0.7.1.2006.04.05 (mswin32)
 4. ruby-postgres 0.7.1.2006.04.05 (ruby)
 5. ruby-postgres 0.7.1.2005.12.21 (ruby)
 6. ruby-postgres 0.7.1.2005.12.21 (mswin32)
 7. ruby-postgres 0.7.1.2005.12.20 (mswin32)
 8. ruby-postgres 0.7.1.2005.12.20 (ruby)
 9. ruby-postgres 0.7.1.2005.12.19 (mswin32)
 10. ruby-postgres 0.7.1.2005.12.19 (ruby)
 11. ruby-postgres 0.7.1.2005.11.27 (mswin32)
 12. ruby-postgres 0.7.1.2005.11.27 (ruby)
 13. ruby-postgres 0.7.1.2005.11.26 (ruby)
 14. ruby-postgres 0.7.1.2005.11.24 (ruby)
 15. ruby-postgres 0.7.1.2005.11.24 (mswin32)
 16. ruby-postgres 0.7.1.2005.11.23 (ruby)
 17. Cancel installation
> 1
Building native extensions.  This could take a while...
ruby extconf.rb install ruby-postgres
checking for main() in -lpq... yes
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for PQsetClientEncoding()... yes
checking for pg_encoding_to_char()... yes
checking for PQfreemem()... yes
checking for PQescapeString()... yes
checking for PQexecParams()... yes
creating Makefile

make
cc -I. -I. -I/usr/local/lib/ruby/1.8/amd64-freebsd6 -I. -DHAVE_LIBPQ_FE_H -DHAVE_LIBPQ_LIBPQ_FS_H -DHAVE_PQSETCLIENTENCODING -DHAVE_PG_ENCODING_TO_CHAR -DHAVE_PQFREEMEM -DHAVE_PQESCAPESTRING -DHAVE_PQEXECPARAMS -I/usr/local/include -fPIC -O2 -fno-strict-aliasing -pipe    -fPIC -Wall -c postgres.c
cc -shared -Wl,-soname,postgres.so -L'/usr/local/lib' -Wl,-R'/usr/local/lib' -L'/usr/local/lib' -Wl,-R'/usr/local/lib' -o postgres.so postgres.o  -Wl,-R -Wl,/usr/local/lib -L/usr/local/lib -L. -lruby18 -lpq  -lcrypt -lm  -rpath=/usr/lib:/usr/local/lib -pthread  -lc

make install

make clean
Successfully installed ruby-postgres-0.7.1.2006.04.06
Installing ri documentation for ruby-postgres-0.7.1.2006.04.06...
Installing RDoc documentation for ruby-postgres-0.7.1.2006.04.06...
$