Well the crash is happening at the point where the perl interpreter has just finished executing the body of a require'd file (the require occurring as part of a 'use'). The interpreter is popping the CXt_EVAL context frame off the context stack (which was pushed on when the require'd file was about to be compiled). One step of popping the context is to decrement the recount of a temporary SV pointed to from within the context struct (which happens to hold the name of the file being compiled - or possibly the package name; can't remember which). The pointer stored in the context struct is obviously corrupt - it looks like part of the context struct has been overwritten with the text "nstance", as has been pointed out.
What the cause of this is, I don't know. Given that you're doing weird stuff with delaying execution, my initial instinct was that the context stack pointer has been decremented and then some other code has pushed a new context frame on, overwriting the eval context - all before the interpreter has actually returned from doing the require, However in this case, I would expect a new context frame (even of a different type than CXt_EVAL) to be mainly full of pointers and the like - not full of literal text. So it looks like a deeper problem with a rouge string pointer somewhere.