The problem is that you didn't include the two magic lines:

use strict;
use warnings;
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If you had you would have seen these indications that Something Was Not Right(tm):

Bear> perl open.txt
flock() on unopened filehandle OUT at open.txt line 9.
seek() on unopened filehandle OUT at open.txt line 10.
print() on unopened filehandle OUT at open.txt line 11.
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