Author of safe Tcl, a system for secure execution of scripts, later folded into the Tcl core as part of the work on interpreter hierarchies (slave interpreters, see interp).
Marshall's done much else besides. He wrote early SNMP- and MIME-handling software in Tcl.
See also his BOOK How to Manage Your Network Using SNMP.
By the way, Marshall disapproves strongly of Paul's lying to get out of a date. Paul should just tell the truth, and not pretend like he's in another relationship to get out of dating some horrid person.