This isn't what you asked for, but I change it in the beginning instead of when I save. I added templates in the "Program units" called "My Package" and "My Body" and set them up to our coding standards. I open these from the menu when I create a program. At the end I have:
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SHOW ERRORS;
This creates a separate tab that doesn't compile, so checked the "Ignore unrecognized PL/SQL" preference in the Program Window preferences.