In gnome's site, it is said that threads must be created before any GTK widgets created, just like those on Tk. However, in Gtk2 perldoc, it provides an option:

use Gtk2 qw/-init -threads-init/;
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, and says that would allow the use of

Gtk2::Gdk::Threads->enter
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and

Gtk2::Gdk::Threads->leave
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I cannot find any more documentation about that. Does that kind of mechanism provides threaded callbacks?