I would consider this a bug, either in the documentation (for not documenting what happens if you combine both capturing and noncapturing components in the split PATTERN)

From perlfunc 5.8.0: 

    As with regular pattern matching, any capturing parentheses that
    are not matched in a "split()" will be set to "undef" when
    returned:

        @fields = split /(A)|B/, "1A2B3";
        # @fields is (1, 'A', 2, undef, 3)

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ihb

Read argumentation in its context!

In reply to Re^5: split and capture some of the separators by ihb
in thread split and capture some of the separators by shemp

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