my starting point was to declare a var for each half of the instruction to be built and to deal with them independently. however, i have trouble with manipulations inside the grammar. (such being akin to trying to force perl to deal with values too big to be int.) e.g. the token "nop" is not recognised (and hence the grammar is incomplete) if i do: 

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"

}

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In reply to Re: Re: Parse::RecDescent for 48bits by bear_hwn
in thread Parse::RecDescent for 48bits by bear_hwn

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