What is happening is as it stands the regular expression is evaluating two characters at a time.Whereas the frame for the matches should be one character. A sloppy fix would be:

while (<DATA>) {
   $i=0 while s/\|\|/\| \|/g; # repeats as many times as is necessary
   print;  
}

As joost rightly says the forward lookahead operation is probably the best way to go.
To make regexes easier to read try using the debug pragma:

use re 'debugcolor'

To get insight into how the regexes do what they do ;)

I'd love to find a solution using the 'c' modifier .. but then I'm not Abigail

--

Brother Frankus.

¤