On grammatical class:

pe'o
forethought flag for mathematical expression (mex) Polish (forethought) operator.
kei'ai
mekso style converter: elementwise application of operator

In definition:

cmavrpe'o
x1 is the selma'o "PEhO".

In notes:

re zei meksota
x1 is a part of Lojban text representing rule 'mex-2' according to the first edition of the book 'The Complete Lojban Language'.