/proc/hascall(Object, text/ProcName)
Arguments:
Object: The object to check.
ProcName (text): The name of the proc.
Returns:
num: 1 if the object has the specified proc; 0 if it does not
/datum/my_thingy/proc/does_something()

/world/New()
    var/datum/my_thingy/thing = new

    if(hascall(thing, "does_something"))
        world.log << "The thing does something!"