yes, of course. This may heavely depends on th OS, i think. in win7 for example there is a PID for every tab open and if you kill such PID the tab only goes in error if is a tab in a group. if you close a 'main' window via kill you kill all windows at same time, and is not a nice thing.
note that 'default browser' is only a facility of an OS not a Perl concept.
There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.