Expressions were done using the conventional infix operators, but all operators had the same precedence and expressions were evaluated from left to right unless there were brackets. Assignment looked particularly odd to most programmers, with the destination on the right, since assignment was just another operator. There were several language features that appear to have existed to allow programmers to produce reasonably well optimised code with what must have been a very primitive code generator in the compiler. These included operators similar to the += etc in C, explicit register declarations for variables, and things even more bizarre than that.
A book describing Mary was printed in 1974. At that date it appears there were working (but not quite complete) compilers for two different Norwegian built minicomputers.
Mary is currently mantained by Kvatro Telecom AS.