First you do a numeric sort. In this case, undef and the strings take on the value zero in a numeric context. Thus, 0, undef, 'aaa', 'AAA', 'ZZZ' and 'zzz' all compare equally and come before the >0 numbers. Then for all the ones above that are numerically equivalent to 0, you do a string comparison; now in string cxontext, undef is treated as the empty string "" and 0 is treated as the one character string "0". Thus they get sorted as undef, 0, AAA, ZZZ, aaa, zzz.
Running with warnings enabled might be illuminating at this point.

Dave.

In reply to Re: Puzzeled about Sorting by dave_the_m
in thread Puzzeled about Sorting by pelagic

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