Very good point... But then again, Windows Metafiles are just that, a dump of GDI api calls
see => http://ed.agadak.net/2008/07/firefox-31-restricts-matches-keywords
For Alpha 1, you can restrict the search to your history by typing "^", or bookmarks with "*", or tagged pages with "+". To make what you've typed match only in the URL type "@", and for title/tags only use "#".