Tk question about -command=>sub{} and Text Insert()

[Panda-X]

Hi all,

Below is my code. With this code, 12345 will show at once
after 5 seconds I click the button.
But what I want is to insert() each number per second.
Is that something I can do like $| = 1 in such case ?

At least, could anybody tell this is the behavior of insert () ?
or it's the behavior of -command => sub {} ?

Thank you very much !
==============================

use Tk;

sub SetButton {
    $_[0]->{mw} -> Button ( -text=>'click me',
        -command => sub { $_[0] ->RollText() }
    )   -> pack ();
}

sub RollText{
    for ( 1..5 ) {
      $_[0] ->{mw}{box} -> insert ( 'end', $_ ) ;
      sleep 1;
    }
}

sub SetText {
    $_[0]->{mw}{box} = $class->{mw} -> Text ( -width => 10 , -height => 10 )
-> pack();
}

sub Build {
    my $self = {} ;
    $self -> {mw} = MainWindow -> new ( -title => 'goodbye world' ) ;
    return bless $self ;
}

my $class = Build ();
$class -> SetText ;
$class -> SetButton ;
MainLoop();