In a BESM-6 disk image I can see bits and pieces of something that looks like a strange interactive scripting language:
[start of disk block] <LET=P11=%X01 <IEQ=P11=%377 <LET=P11=1 <END <LET=P12=0 <REP=META=P12=%P11 <ADD=P12=1 <<MO2 <<K31 <<MO5 <<K35 ... [a dozen more <<MOn and <<Knn lines] <MES= ROUND %P12 ENDED [originally in Russian] <LAB=META [end of file marker, zeros to the end of the block]
Here one can guess that
<LET is an assignment operator,
<IEQ is a conditional,
<REP is a loop up to a label,
<MES means "message", the % sign in a message text is an interpolation operator, etc.
<< lines are unclear.
Another example I've found is (with texts translated)
<МЕS= <МЕS=*** IBM TAPE VERIFIER *** ( 03.02.89 ) <МЕS= <GЕТ=11=VOLUME- <GЕТ=13=RECORD DENSITY (8, 32, 63)- <GЕТ=14=TAPE DESIGNATOR (MAX. 21 CHARS.)- ...
As all the keywords are in English, a Western prototype is likely.
In pieces of the documentation in Russian I was able to find, this functionality is called "interactive macrogenerator" (just like that, without a proper name). Searching for that in English finds a few documents about TRAC, which is a different language.
Searching in Russian finds a page which mentions
IEQ, etc. The page title suggests that the name of the language was likely PAGEN, and the links below, mentioning Soviet DEC clones - that it could have stemmed from DEC.
Searching for 'pagen', or even "!pagen +DEC" leads nowhere.
What was the language called PAGEN which used less-than signs to start keywords and equal signs as separators?