This recent post on the Gtk-perl mailing list suggests you need to use the perli11ndoc tool from Glib::Object::Introspection: https://mail.gnome.org/archives/gtk-perl-list/2018-February/msg00008.html.

I have not tried it, though, as I do not have Gtk3 installed.

In reply to Re: No docs on the GTK+3 module? by swl
in thread No docs on the GTK+3 module? by GnomoP

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