How Opera `tively processed regexps

It is a trick to avoid redundant backtracking.

From release 10.00

That's what these “tricks” are. See a simple example:
javascript: alert (/ (t +) {2} /. test ('tt'));

IE6, IE8: true
Firefox: true
Safari: true
Chrome: true
Opera9: true
')
Opera10: false

Be on the alert,% username%.