SAS/IML 12.3 is essentially a maintenance release of SAS/IML software that runs on SAS 9.4.
For more information, see the software product page for SAS/IML.
SAS/IML 13.1 is a major release that runs on the first maintenance release of SAS 9.4 and later releases.
Here are some of the new features and enhancements:
enhancements to the SAS/IML language syntax:
The NEXT keyword now supports expressions.
The STOP and ABORT statements now accept a default message that is displayed in the SAS log.
The parentheses in the RETURN statement are now optional.
new support of the Tweedie distribution by the RANDGEN subroutine
new statistical functions, subroutines, and modules: ...