I obviously hadn't quite mastered combining positive lookahead and non-greediness (selflessness?) yet. Until now my solution was to use two statements: 
    s{\[_(CELL|COLHEAD)_\] (.*)}{<$1>$2</$1>}g;
    s{\s*\[_(CELL|COLHEAD)_\]\s*}{</$1><$1>}g;

[download]
Here it's more complicated because there's several of these tags. It's lamer and slower than yours, so I'll gladly change it, thanks!

Pauses to think for a while... Hm, with that extra twist I just introduced (not fair, I know), maybe the two-step version isn't slower. Lookahead on something it doesn't know yet could get tricky, maybe. 

    s,\[_(CELL|COLHEAD)_\]\s*(.*?)\s*?(?=\[_\1_\]|$),<$1>$2</$1>,g;
But it seems to work fine, and I don't think I care about speed anyway.

In reply to Re: Re: Transforming strange format to XML by Tortue
in thread Transforming strange format to XML by Tortue

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