I have some students (in introductory programming course) who see programming language as a set of magic spells, which must be cast in order to achieve some effect (instead of seeing it as a flexible medium for expressing his idea of solution). They tend to copy-paste code from previous similarly sounding assignments without considering the essence of the problem.

Can anyone recommend some exercises or analogies to make those students more confident that they can and should understand the structure and meaning of each piece of code they write?