I have just read up on two's complement and one's complement through the link to wikipedia provided by haukex. I had not realised there was a two's complement representation as well as operation, and when I suggested the masking ideas, that the numbers being masked to produce the decimal representation were in two's complement representation. It just seemed to work.

I may have been a little off the mark, when suggesting these were some kind of unused integers, yet I feel it is too early to dismiss the idea as just an outdated one's complement runoff.

I really got a lot out of this thread and the responses from everybody have been very helpful and informative. It is exciting to find out new stuff and expand my knowledge. I try to keep it Perl, but the nature of computers is that it is all related in some manner.

Perl may be DWIM, but WDIM? :)