Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!fletcher
From: fletcher@cs.utexas.edu (Fletcher Mattox)
Newsgroups: comp.mail.misc
Subject: Re: Precedence of ! and % (was: sending from MIT to Ireland)
Message-ID: <16476@cs.utexas.edu>
Date: 4 Jan 91 00:20:39 GMT
References: <PCG.90Dec26192702@teachk.cs.aber.ac.uk> <aynnmf.356@wang.com> <Jan.3.14.53.11.1991.1641@turbo.bio.net>
Organization: Dept of Computer Sciences, UTexas, Austin
Lines: 10

RFC1123:
	... It is suggested that "%" have lower precedence
	than any other routing operator (e.g., "!") hidden in the
	local-part; for example, "a!b%c" would be interpreted as
	"(a!b)%c".

The parentheses can be interpreted mathematically.  
I.e. the operands of ! should be evaluated first, thus giving !
higher precedence than %.  I suspect this is what the authors
had in mind.  I agree it is confusing.