The default version is pro. To get to another version,
from the unix prompt type:
stardev (e.g. for dev)
All the corresponding environment variables will then point to dev.
To see what command maps to what version look in $STAR_ROOT/packages.
Versions dev, new, pro etc. are links pointing to release directories
SL*.
For example, it is currently:
dev --> 98f new --> 98d pro --> 98e frozen --> old --> 98b
To go to a particular release that doesn't have one of the above
release directories, type (e.g. for 98a)
  starver 98a
To see what version you're set up to use, type 'which staf' or 'STAR_LEVELS'.