Thanks, guys!

The reason why I built up @chrnums and @coords first is because there are also such things as chrX and chrY, so the next step would be to include a small "if" within the code that would push, say, 100 to @chrnums in place of "X" and 101 in place of "Y" for chrX and chrY to be put in the list last.

So I just thought it'd be faster and more readable to do it in two steps.

From what you are suggesting I understand that it is more efficient to build just one sorting criterion instead of two and then ask Perl to sort the thing as a string - am I right? But then, will Perl understand that, say, chr10, should go after chr5?

Thanks again!