YCP, originally planned as a functional language, always did dynamic (i.e. runtime) binding of variables. Although useful in many cases, it's quite puzzling for someone used to “imperative” languages. So you could well program the following block and get an unexpected result.

{
   integer x = 42;

   define f() ``{ return x; }

   ... // lots of lines

   x = 55;

   return f();  // will return 55 because of runtime binding of x!
}
	

Another widely misused feature is to include global definitions. While there was no alternative as long as include was the only referencing instrument, this is certainly not a good programming practice in view of speed and memory considerations.