AoC 2021 day 24, writing programs (Perl) that write programs (C Macros) that write programs (C)

#!/usr/bin/perl

use strict;
use warnings;
use v5.10;

my $comment = <<'END';
END

# compile input down to C code. We'll need a support function for
# implementing 'inp', so, why not actually write everything with
# macros...

my $preamble = << '__C';

#include <stdio.h>

#define INP(a)     a = *(input++)
#define ADD(a,b)   a += b
#define MUL(a,b)   a *= b
#define DIV(a,b)   a /= b
#define MOD(a,b)   a %= b
#define EQL(a,b)   a = (a == b) ? 1 : 0

long program(long *input) {
    signed long w = 0;
    signed long x = 0;
    signed long y = 0;
    signed long z = 0;

__C

my $postamble = << '__C';

    return z;
}

// increments number, returning false on overflow
int increment(long *num) {

    int digit = 9;
    while (digit >= 0) {
        num[digit]++;
        if (num[digit] < 10) {
            return 1;
        }
        // carry to next higher digit
        num[digit] = 1;
        --digit;
    }
    return 0;
}

int main(int ac, char** av) {
    long low[14] = { 1, 4, 9, 1, 1, 6, 7, 5, 3, 1, 1, 1, 1, 4 };
    // while(increment(low)) {
    // }
    printf("low x = %d\n", program(low));
    long high[14] = { 6, 9, 9, 1, 4, 9, 9, 9, 9, 7, 5, 3, 6, 9 };
    // while(increment(high)) {
    // }
    printf("high x = %d\n", program(high));
    return 0;
}

__C

my @clines = ();
foreach ((<>)) {
    chomp;
    if (/^inp (\w)/) {
    push @clines, "INP($1);";
    } elsif (/^(\w+) (\w) ([wxyz]|-?\d+)/) {
    my $instr = uc $1;
    push @clines, "$instr($2,$3);"
    } else {
    die "parse error: $_\n";
    }
}

say $preamble;
say join "\n", @clines;
say $postamble;