sub handler {

my $timer = $mw->repeat(100,\&sighandler );

sub sighandler {

my $data = $port->lookfor;
return unless $data;
# do stuff
print STDOUT "$time Message Received: (" . $data . ")\n";

if ($data =~ /OF/) {
$signalblock100->configure(-image => $mw->Photo(-file => 'picture.jpg'));
}
$port->lookclear;
}

}