I found a workaround:
(self copyReplaceTokens: '||' with:'@') subStrings:'@'
Where the copyReplaceTokens: with: message replaces the double pipes. then the subStrings:'@' gives me the result I was looking for:
#(' Middle-left-cell ' ' style="width: 14em;" | Middle-center-cell ' ' Middle-right-cell')
-- Sent from: http://forum.world.st/Squeak-Beginners-f107673.html