sub exec_internal_sub
{
    my ($sub_ref, @sub_args) = @_;
    try
    { 
        $sub_ref->(@sub_args);
    }
    catch
    {
        my $E = shift;
        throw Error::Simple($E);
    };
}

sub interface_sub
{
    exec_internal_sub(\&internal_sub1, $arg1, $arg2);
    exec_internal_sub(\&internal_sub2, $arg1, $arg2, $arg3);
}