x=> parses as ((MEQUAL SIMP) |$x| $>)
There are in fact TWO problems here (though probably
from the same source). First of all, the expression is
syntactically illegal, just like x=+, x=<, etc. Secondly,
the parser is generating $>, which should never be
generated. The three forms of > are &> (string ">"),
mgreaterp (verb), and %greaterp (noun).