If "allow one to use system commands as if they were previously declared functions" is your criteria, then things like Symbolics Genera, PERQ POS and Xerox Star

If "allow one to use system commands as if they were previously declared functions" is your criteria, then things like Symbolics Genera, PERQ POS and Xerox Star/Alto predate it by even more. This is not a new or original idea to Perl.