Looks like it's documented in open and creates a (useless in this case) anonymous temporary file.. (Try printing $fh->tell for example.) If the 3rd arg is undef, "opens a filehandle to a newly created empty anonymous temporary file. (This happens under any mode, which makes +> the only useful and sensible mode to use.)"

In reply to Re: open undef by ForgotPasswordAgain
in thread open undef by morgon

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