Hi,
your mod-file runs without problems on my machine (irf=1, i.e. for one period makes no sense, though). I would advise you to check, if you installed Dynare correctly and in particular if the Dynare path has the highest priority in the Matlab paths. It might be that there is another function called irf that has a higher priority, e.g. from the econometrics toolbox.
Thank you, that was exactly my problem. I have saved my file in a separate Dynare folder, it worked after I saved the file in the folder where I originally installed Dynare.