#!/usr/bin/perl -w
use Tk;

my $mw = MainWindow->new(-title=>"Demo");

my $HlpBttn = $mw->Button(
    -text    =>"Make NEW Window",
    -command =>  [ \&makeWindow, $mw ], # calls makeWindow and passes $mw as the first argument
);
                       
$HlpBttn->pack(-padx =>60, -pady =>10);


MainLoop;

sub makeWindow {
    my $parent = shift;
    my $win  = $parent->Toplevel(-title=>'new window');
    my $Bttn = $win->Button(
        -text=>"CLOSE this window",
        -command=>  [ 'destroy', $win ],  # calls destroy on $win
    )->pack(
        -padx =>60,
        -pady =>10,
    );
}
__END__