[7.9]  Are there $variables that can be used in field default values, that do not require code customization?

I'm looking to set up default values on multiple fields that call $LBL_FIRST_NAME from the contact so it starts off with their name (if there is one) and can be changed by the end user.  

Example:  If an end user creates a call for client John Doe, the default subject line would read "Call with John", where 'John' is called by that $variable.  

Problem: I don't know the correct syntax for how to pull this off, or if it is even possible without code customization.  

Thank you in advance!