Provide validation mechanism for variable input

[Tony Skalski]

Provide a validation mechanism for variable input, to protect ourselves from users. A simple method would be to run a script on input. The script could have a special name like “validate_mds_var{1-9}.sh”. If the script existed, it would run for that variable entry. The script could provide a text error message if the variable fails validation that would be displayed to the user.