SWAP$

[hutch--]

> i think JJ has the right idea - swap pointers, instead

Thats fine if they are in an array of pointers, what about in a text file ?

Even better, use a 1 pass hash replace with only the swap words loaded in the hash table.  :bg

[GregL]

... but these operations are very slow...

Geez jj, why are you so obsessed with speed?  So, if those operations are not super fast, we can't use them?  Bologna.  I think allocating new strings like that would be the best way to do it.  And they would be fine for general purpose procedures.