$main->Button(
    -text    => "Save",
    -command => sub {
         my @capture=();
         my ($x0,$y0,$x1,$y1)=$canvas->bbox('all');
         @capture=('-x'=>$x0,'-y'=>$y0,-height=>$y1-$y0,-width=>$x1-$x0);
         $canvas -> postscript(-colormode=>'gray',
                   -file=>$0.'.ps',@capture);
                }
    )->pack;



MainLoop;