: if you.race() == "Hill Orc" then
priest = Beogh
: else
priest = Yredelemnul
: end

Note that none of the options listed under "Starting Screen" (section 1)
can be set conditionally.  This is because the options files are
actually read in twice: once before character creation with Lua turned
off, and a second time after character creation with Lua turned on.  If
you attempt to set a starting-screen option conditionally then the value
furthest down in the options file will be used regardless of what
conditions you set.
The above caveat applies to the "wiz_mode" option as well.