File::CounterFile - Persistent counter class

     use File::CounterFile;
     $c = File::CounterFile->new("COUNTER", "aa00");

     $id = $c->inc;
     open(F, ">F$id");

    This module implements a persistent counter class. Each counter is
    represented by a separate file in the file system. File locking is
    applied, so multiple processes might try to access the same counters at
    the same time without risk of counter destruction.

    You give the file name as the first parameter to the object constructor
    ("new"). The file is created if it does not exist.

    If the file name does not start with "/" or ".", then it is interpreted
    as a file relative to $File::CounterFile::DEFAULT_DIR. The default value
    for this variable is initialized from the environment variable "TMPDIR",
    or /usr/tmp is no environment variable is defined. You may want to
    assign a different value to this variable before creating counters.

    If you pass a second parameter to the constructor, that sets the initial
    value for a new counter. This parameter only takes effect when the file
    is created (i.e. it does not exist before the call).

    When you call the "inc()" method, you increment the counter value by
    one. When you call "dec()" the counter value is decrementd. In both
    cases the new value is returned. The "dec()" method only works for
    numerical counters (digits only).

    You can peek at the value of the counter (without incrementing it) by
    using the "value()" method.

    The counter can be locked and unlocked with the "lock()" and "unlock()"
    methods. Incrementing and value retrieval is faster when the counter is
    locked, because we do not have to update the counter file all the time.
    You can query whether the counter is locked with the "locked()" method.

    There is also an operator overloading interface to the File::CounterFile
    object. This means that you might use the "++" operator for incrementing
    the counter, "--" operator for decrementing and you can interpolate
    counters diretly into strings.

    Copyright (c) 1995-1998,2002,2003 Gisle Aas. All rights reserved.

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

    Gisle Aas <>