How to dynamically load a movieclip from the library from a string

Throughout different times in my app I have to load, and then later on delete, a series of movieclips from the library.They all have the prefix “mc_”.

var str_movieclip = "mc_" + get_current_movieclip_name();
//ex: mc_person1
var mc1:MovieClip = new str_movieclip;

Shows error:

TypeError: Error #1007: Instantiation attempted on a non-constructor.

How do I do this?