int seqDiff32 ( SV *s1, SV *s2 ) {
    STRLEN bytes1, bytes2;
    char *p1, *p2;
    STRLEN dwords;
    STRLEN lastBytes;
    U32 *up1, *up2;
    int i;

    p1 = SvPV( s1, bytes1 );
    p2 = SvPV( s2, bytes2 );
    if( bytes1 != bytes2 ) return 0;

    up1 = (U32*)p1;
    up2 = (U32*)p2;
    dwords = bytes1 >> 2;
    lastBytes = bytes1 % 4;
    p1 += dwords << 2;
    p2 += dwords << 2;

    while( dwords-- ) {
        if( *up1 != *up2 ) {
            for( i = 0; i < 4; ++i ) {
                char c1 = ( (char*)up1 )[ i ];
                char c2 = ( (char*)up2 )[ i ];
                if( c1 != c2 && c1 != 'N' && c2 != 'N' ) {
                    return 0;
                }
            }
        }
        up1++; up2++;
    }

    for( i = 0; i < lastBytes; ++i ) {
        char c1 = ( (char*)p1 )[ i ];
        char c2 = ( (char*)p2 )[ i ];
        if( c1 != c2 && c1 != 'N' && c2 != 'N' ) {
            return 0;
        }
    }
    return 1;
}