sub interface_sub
{

    try
    { 
        internal_sub1($arg1, $arg2);
    }

    catch Error with
    {
        my $E = shift;
        throw Error::Simple($E);
    };

    try
    { 
        internal_sub2($arg1, $arg2, $arg3);
    }

    catch Error with
    {
        my $E = shift;
        throw Error::Simple($E);
    };
}