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From: Bart Schaefer <schaefer@brasslantern.com>
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Date: Thu, 15 Oct 2015 22:05:45 -0700
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Comments: In reply to Mikael Magnusson <mikachu@gmail.com>
        "Re: backreferences" (Oct 16,  6:11am)
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To: Zsh Users <zsh-users@zsh.org>
Subject: Re: backreferences
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On Oct 16,  6:11am, Mikael Magnusson wrote:
}
} As a sidenote, (^foo)* is always useless to write, since (^foo) will
} expand to the empty string, and then the * will consume anything else.

Minor correction ... (^foo) will be the empty string only if the tested
string begins with "foo".  But then * will consume the "foo", making
the (^foo) useless.  Conversely if the string does not contain "foo" at
all, (^foo) will consume all of it and * will match the empty string.

However, (^foo)(*) could be very useful with backreferences, because
(^foo) puts everything up to "foo" into $match[1], and then (*) puts
from "foo" to the end into $match[2].  Which happens to be a lot like
what Ray was trying to accomplish.

} A useful way to think of (^foo) is a * that will exclude any matches
} that don't match the pattern foo.

Yes.  There's a really long explanation of this in Etc/FAQ 3.27.