I think you want look-ahead matching here: 
s/\|(?=\|)/\| /g;

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See also perldoc perlre though I'll admit it's not the easiest of topics :-) 
-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.

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In reply to Re: Regex Backtracking by Joost
in thread Regex Backtracking by Anonymous Monk

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