I'm not running Linux so I can't really test this, but something like this should do what you are seeking.

**Untested**

use strict;
use warnings;
use Tk;
use Tk::ROText;
use Lirc::Client;
use IO::Select;

my $top = MainWindow->new;

my $text = $top->ROText(
    -background => 'white',
)->pack;

my $lirc = Lirc::Client->new( 'progname' );

my $select = IO::Select->new();

$select->add( $lirc->sock );

$top->repeat( 200, \&getcodes );

MainLoop;

sub getcodes{
    if( my @ready = $select->can_read(0) ){ 
        my @codes = $lirc->next_codes;
        $text->delete( '1.0', 'end' ) if @codes;
        for my $code (@codes){
            $text->insert( 'end', "$code\n" );
            #do whatever else you want with $code
        }
    }
}
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