The reason you're getting the zero-length elements is that you have two delimiters that follow eachother. Inbetween those delimiters there's nothing, and therefore you get a string holding nothing.

Example:

    $_ = 'XABX';
    print "<$_>" for split /A|B/;

    __END__
    <X>
    <>
    <X>
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Step by step, it goes a little like this:

    'X' . 'A' . 'BX' # 'A' matched.
    'BX'             # 'A' removed, 'X' returned.
    '' . 'B' . 'X'   # 'B' matched.
    'X'              # 'B' removed, '' returned.
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ihb