OK, I thought I had solved it, but for some reason I started Calibre up today and wanted to check the regexp before adding the next folder, but again everything ends up in the Title field.
This is the regexp: (?P<author>.+)--(?P<title>.+) \((?P<publisher>.+) (?P<published>[0-9])\)
This is the test file name: Agaian S.S.--Hadamard Matrices and Their Applications (Springer 1985).pdf