To be honest, your code really doesn't make much sense. Here's how I'd do it:

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

@list = sort { substr($a, 0, 8) cmp substr($b, 0, 8) } @list;
[download]

At the end of this code, @list contains the data in sorted order.

Update: Ovid is right, of course. Corrected.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you don't talk about Perl club."