I made $stn a hash ref because this isn't going to work:

$seg{$lname} = { 'header'   => \@hdr,
                 'stations' => \%stn, };
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You'll find that the header will always point to the same array. The same will be true for stations - all of them will be the same hash.

However, if you make the stn hash a hash ref, then this will work:

# time to save stn and headers:

$seg{$lname} = { header => [ @hdr ], stations => $stn };
@hdr = ()
$stn = undef;
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Note the square brackets around @hdr - this will create a new array.