I think the first time I saw REXX was in IBMDOS 7 (might have been IBMDOS 6. I was astounded. A real freaking scripting language in DOS. was a rocking advantage, back then. It put 'bat' files to ugly shame. Since that time, it is only with MS Powershell that Microsoft has finally developed a decent tool for scripting.
IIRC, that was called PC DOS 7. And also came with a copy of Stacker.