I personally prefer to use custom commands for this.
For example (Settings->Customize->Commands->User->Add)
- Command1:
name = g
template = query
tip = google search
command:"C:\Program Files\Opera 9\opera.exe" "https://www.google.com/search?q=&query&
- Command2:
name = map
template = query
tip = google maps search
command:"C:\Program Files\Opera 9\opera.exe" "https://maps.google.com/maps?q=&query&"
Next, drop a commands field from (Settings->Customize->Commands->Tools) in your GUI.
Next you can type g or map followed by your query in the command field. E.g.:
g test
g "test query"
map europe
etc...
For meta searches just insert multiple searches into the body of the custom commands.