Documentation for infix <=, infix ≤ assembled from the following pages:

Language documentation: Operators §

From Operators

(Operators) infix <=, infix ≤ §

multi sub infix:«<=»(Int:D, Int:D)
multi sub infix:«<=»(Num:D, Num:D)
multi sub infix:«<=»(Real:D, Real:D)

Numeric less than or equal to operator.

Coerces both arguments to Real (if necessary); returns True if the first argument is smaller than or equal to the second.