Not to beat a dead horse too much, but is there any reason not to simply sort the list as it's read (which conserves memory, if THAT matters here)? To wit:

open DATABASE, $mydata or die "Can't open $mydata: $!\n";
flock DATABASE, LOCK_EX or die "Can't lock $mydata: $!\n";
my @list = sort <DATABASE>;
#  NOTE    ^^^^
close DATABASE; # which also unlocks it
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dmm

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