use warnings;
use strict;
use Tk;


my $mw = new MainWindow;
$mw->geometry("200x200");
my $frame = $mw->Frame()->pack;

my $textbox = $frame->Scrolled('Text',
	-scrollbars => 'soe',
	-foreground => 'blue',
	-background => 'white',
	-wrap => 'none',
  )->pack;
$textbox->insert('end', "This is scrolled widget.\nThis is scrolled widget.This is scrolled widget"); 

my $wrapmonitor = $textbox->cget('wrap');
$textbox->repeat(100, 
    sub { 
        if ( $textbox->cget('wrap') ne $wrapmonitor ){
            $wrapmonitor = $textbox->cget('wrap');
            mycallback($wrapmonitor) #whatever
        }
    }
);

MainLoop;

sub mycallback {
    print shift, "\n";
}