... a standard alpha-numeric sort produces the correct order.

If by "standard alpha-numeric sort" you mean a lexicographic or "asciibetic" sort (the default sort of sort), this is unfortunately not the case: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @ra = qw(1.2.1  1.2.2  1.2.3  1.2.10  1.2.11  1.2.20  1.2.21);
 my @sorted = sort @ra;
 dd \@sorted;
"
["1.2.1", "1.2.10", "1.2.11", "1.2.2", "1.2.20", "1.2.21", "1.2.3"]

[download]
The digit sub-fields need to be "normalized" in some way, e.g., by being zero-padded for a lexical sort comparison ('01.02.02', '01.02.20'), or by being converted to a standard number for numeric comparison (1.002_002, 1.002_020).

Sadly, the example data of the OP does not make this problem evident.

Update: I posted this reply before I saw Corion's post, which addresses the same problem and has a number of informative links.

Give a man a fish:  <%-{-{-{-<

In reply to Re^2: Advanced Bubble Sort by AnomalousMonk
in thread Advanced Bubble Sort by Anonymous Monk

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