You can use a zero-width positive look behind, like this: 
use strict;
use strict;
while (<DATA>) {
    s/(?<=\|)\|/empty|/g;
    print;
}


__DATA__
|a|||
||||
|||a|

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I usually find it easier to maintain code that uses split though.

In reply to Re: pipe delimited file problem by imp
in thread pipe delimited file problem by lakeTrout

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