Code:

#!/usr/bin/env perl

use strict;
use warnings;
use Tkx;
use utf8;

my $main_window = Tkx::widget->new(".");
$main_window->g_wm_title("Authorization");
$main_window->g_wm_resizable( 0, 0 );

my $label_of_telephone_or_email = $$main_window->new_ttk__label(-text 
+=> "Telephone or email:");
$label_of_telephone_or_email->g_pack;

Tkx::MainLoop();
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Error:

Can't locate object method "new_ttk__label" via package "."