ensembles and number of files

The help files for ensembles 2.8.4 ENSSTAT - Statistical values over an ensemble states multiple files can be used as below

cdo ensmean infile[1-6] outfile
  cdo enspctl,50 infile1 infile2 infile3 infile4 infile5 infile6 outfile

I wish to do a 30-year (1961-1990) ensemble where each year is in a separate file

cdo ensmean infile_19[61-90].nc outfile     fails
  cdo ensmean infile_19??.nc outfile          quick and dirty works but it has extra years

cdo ensmean infile_19[6-8][1-9].nc infile_19[7-9]0.nc outfile        also works but is untidy

It seems the filename substitution can only handle one character (at a time) or is there a way to do this that's neater than the above?

Thanks

Hi Miles,
I think you can try this:

cdo ensmean -selyear,1961/1990 -cat filein*.nc fileout.nc

This code calls all the files, but selects only those years

(1-1/1)

CDO