x
x
x


Do so in a way which:

 does not involve string manipulation of the input source code
 is plausibly extensible to a runtime-chosen set of bindings rather than just x
 does not make x a global variable


or note that these are impossible.



See also

 For more general examples and language-specific details, see Eval.
 Dynamic variable names is a similar task.


 
say evalWithX("x**2", 2)
say evalWithX("x**2", 3.1415926)
 
::routine evalWithX
  use arg expression, x
 
  -- X now has the value of the second argument
  interpret "return" expression
 