Funciton (186 bytes in UTF-16)
╔════════════════════════════╗ ║1934282307508088037380718711╟ ╚════════════════════════════╝
This program prints “world”.
Any substring you remove from this will stop it from being a complete box, which the parser will complain about — with only one exception: removing the entire middle line, leaving this:
Doing so removes the dangling end on the right (the output). This is no longer a valid program. It is simply an empty comment, but the parser expects a program with exactly one output:
Error: Source files do not contain a program (program must have an output).
Therefore, this program is pristine.