use Parse::RecDescent;
$new_grammar = q
{

# perl int is limited to 32 bits
{
        my Instruction_upper;
        my Instruction_lower;
}

program_body :  instruction(s)

instruction :   { Instruction_upper = 0;
                        Instruction_lower = 0; } <reject>
        |       nop_cmd
        |       repeat_cmd

# the nop cmd command

nop_cmd :     nop ';'
                        { Instruction_upper = 0;
                                Instruction_lower = 0;
                        }

# the repeat command

repeat_cmd :    repeat '=' hexnum ';'
                       { Instruction_upper = 0;
                               Instruction_lower = (0x7c000000
                                       | ($item[3] & 0x0FFFF)
                                       );

nop :           "nop"

}