The ordering of output isn't quite what you wanted, but that can't be helped with a hash, since it doesn't preserve the order in which you insert the elements.

That is, it could only be helped if you take the trouble to specify a non-canonical order external to the hash, e.g.:

my @key1_order = qw/AB PL B/;
...
foreach my $key1 ( @key1_order ) {
   ...
}
[download]

or assign sortable values within the hash (which could be worked into the hash-creation process):

$coord_{AB}{order} = 1;
$coord_{PL}{order} = 2;
$coord_{B}{order} = 3;
...
foreach my $key1 ( sort { $coord_{$a}{order} <=> $coord_{$b}{order} } 
+keys %coord_ ) {
   ...
}
[download]