open my $can_bus, "./receivetest |"
    or die "Couldn't read from CAN bus: $!";
my %last_value;
while( <$can_bus>) {
    if( /^(........:...) (........) (.*)$/ )
      
        my( $something, $id, $payload)= ($1,$2,$3);
        $last_value{ $id }= $payload;

        system('clear'); # clear screen

        # print the table
        for my $id (sort keys %last_value) {
            print "$id\t$last_value{ $id }\n";
        };

    } else {
        warn "Ignoring unknown line:";
        warn $_;
    }; 
};