<= function compares numbers according to "less than or equal" predicate. Each (overlapping) pair of the numbers is compared by it. The result is true if all compared pairs satisfy comparison. Note that complex numbers cannot be compared.

(<= 1 2) => T
(<= 2 1) => NIL
(<= 2 2.001) => T
(<= 2 2) => T

(<= 1234567890123456789 9876543210987654321) => T
(<= 1 2 3 4 5) => T
(<= 1 2 4 3 5) => NIL
(<= 1 2 4 4 5) => T
(<= 3/4 7/9) => T
(<= 5) => T