# MATLAB: Does an “if does not contain operator” exist

function

I am trying to write a function where the input must be entered in radians. My idea was to make the function return if the input does not contain "pi". Is there a way to do this?
ex. if you wanted to enter 90 you have to enter pi/2
Thanks

d = input('Input angle in radians [0 <= x <= 2*pi]: ')