You could try to find out whether it is the perl script or swift that is producing the error.

Either use the perl built-in debugger or a real debugger or simply 'strace' (if you are on linux) to find out the exact place your program gets killed.

If you have a version control system in use, find out what changed from last week. If not, you know now why it is a good idea to have one

If someone else installed updates on your machine, find out if one of the modules or other software your script is using got updated