Thanks for your help. After some trial and error, I found the following workaround to the bug: 
$ff = Firefox::Application->new(
  launch => '/Applications/Firefox.app/Contents/MacOS/firefox',
);
$ff->quit( restart => 1 ); # restart
sleep 2;

[download]

This launches a new FF application no matter what, then restarts it. Then I found you have to sleep for a bit before you can call WWW::Mechanize::Firefox->new and go to work browsing in the tab.

If there is a way I can help you troubleshoot this, let me know. I've got a spare mac and I can give you control over it in a guest account via vnc. Maybe that would work.

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In reply to Re^2: WWW::Mechanize::Firefox throwing error when launching a new Firefox instance on Mac by nysus
in thread WWW::Mechanize::Firefox throwing error when launching a new Firefox instance on Mac by nysus

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