Editing System/Library files with Property List Editor (PLE)

For those who don't want to read through the comments, it was a pretty simple fix after Mark gave me a bit of insight.

Initially, I wrote the vmstatus_startup script to call VM.sh which would then continually refresh the perl script (every 5 seconds). I was attempting to call the shell script from launchctl which just adds layers of complexity.

Instead, calling the perl script directly from the .plist and giving the keep alive key allowed it to run constantly after boot.

Finally, I had to make sure to add the perl directory to the .plist above the location of the script since launchd doens't have a PATH the same way a user does.

You need read/write permissions to the containing folder as well as the plist itself for Xcode to modify the file in place.

A workaround for this if you are unable to change the permissions of the containing folder is to copy the file out, edit it, then copy it back over the top of the existing file. Alternatively, you can use a different property list editor such as the CLI ‘defaults’.