This is the script I've been using in order to replace creationd id. perl -pi.bak -e 's{creationid=".+?"}{creationid="Simon Simonsen"}g;' file.xml
This works for me, if file.xml contains only the string you provided above. Can you try to whittle your ~1 GB file down to a simpler test case that fails, e.g. by bisecting it? Doing so may prove instructive in identifying the problem; alternatively, it'll make it easier for us monks to help you if we've got both an "it works" case and a "it stops working if I do this" case.
