# set DEBUG to 1 in package main
% setenv DEBUG main
% perl foo.pl

# set DEBUG to 5 in package main
% setenv DEBUG main=5
% perl foo.pl

# set DEBUG to 2 in package main and 3 in package Foo
% setenv DEBUG Foo=3,main=2
% perl foo.pl

# set DEBUG to 99 in all packages
% setenv DEBUG all=99
% perl foo.pl