~= is available since version 1.0.0.
~= operator consumes three parameters from the top of the stack, two operands p1 and p2 and a tolerance factor lambda,
and pushes onto the stack true if |p1-p2| < lambda, i.e. the difference between the two operands is lesser than lambda.
All parameters must be of numeric types.
~= is useful when making comparaisons between doubles, where floating point operations generate rounding errors.