The tab should automatically close once your $mech object goes out of scope.

If you want to force the closing of the tab, you can undef your $mech object:

undef $mech;
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What is your use case for closing the tab? I think the Chrome API allows for closing a tab, but I didn't implement it, as I didn't see a use case.

Update: The driver object already has a way to close the tab and you can use it as:

    $mech->driver->close_tab( $mech->tab )->get
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... but that will leave your $mech object without a tab. This is not always what you might want.