[ddg://WWW::Mechanize::Firefox tab]
[ddg://WWW::Mechanize::Firefox active tab]
[ddg://WWW::Mechanize::Firefox switch tab]
[ddg://site:search.cpan.org WWW::Mechanize::Firefox switch tab] 

##</code><code>##

activate => 1,  # bring the tab to the foreground
autoclose => 0  # to prevent autoclosing of the Tab
->closeTab
tab => 'current',
->activateTab
->autoclose_tab
->tab
See also Firefox::Application for how to add more than one tab and how to manipulate windows and tabs.