use strict;
use Inline C => <<'__C_CODE__';
SV*
b2i(int value) {
    AV *out;
    int i;

    out = (AV *)sv_2mortal((SV *)newAV());
    i = 0;
    while (value > 0) {
        if (value & 1)
            av_push(out, newSViv(i));
        ++i;
        value >>= 1;
    }
    return((SV *)newRV((SV *)out));
}

__C_CODE__

my $ridx = b2i(12345);
print "@$ridx\n";