Well, technically the OP does say "surrounded", ...

Actually not.

And the examples given do not indicate this possibility either.

Perhaps more important is that "reversible bracketing" doesn't really make much sense. Consider 

foo < foo > foo < foo < foo > foo > foo < foo < foo > foo < foo > foo 
+> foo
123 |.....|.....|     |.....|     |.....|     |.....|.....|.....|     
+  123
                |.................|     |.............................
+|

[download]

Can you conceive of an application where this would make sense?

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
The "good enough" maybe good enough for the now, and perfection maybe unobtainable, but that should not preclude us from striving for perfection, when time, circumstance or desire allow.

In reply to Re^5: Match a pattern only if it is not within another pattern by BrowserUk
in thread Match a pattern only if it is not within another pattern by punkish

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