Thanks, khkramer (and others!) for the responses.

The plot thickens. I'm ashamed to admit I had only assumed the sort operation was to blame for the out of memory error, but it turns out that the sort finishes successfully, and the operation that's choking is really

print AP_LIST Data::Dumper->Dump([\@list], [qw(*list)]);

I'm using ActiveState so I checked the mailing list, and it turns out this is a bug that was reported to ActivePerl mailing list several weeks ago.

Sorry to have dropped a red herring of sorts <grin> but thanks again for the feedback.

Josh