From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 11 Jan 2013 12:44:21 +0100
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From: Rudolf Sykora <rudolf.sykora@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] How to do this with [acme | sam | sed ] ?
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On 11 January 2013 12:19, Peter A. Cejchan <tyapca7@gmail.com> wrote:
> # remove outermost pair of braces:  abcd(x+(y-z))efgh  --> abcdx+(y-z)efgh

This, I believe, can't be achieved only with regexps. I'd write a
small external program and use it as a filter.

> # prefix to postfix operator: ++i --> i++
>          [ Edit s/\+\+[a-zA-Z]+[0-9a-zA-Z]*/&++/ Edit s/\+\+/d]

using the \1 (used to be undocumented on plan9) may be sometimes easier
Edit s/\+\+([A-Za-z]+[A-Za-z0-9])*/\1++/

Ruda