Usage: @np <pref>

 Finds an appropriate new prefix to use, given the files
 you already have in your directory.
 Use this script to automatically create a valid prefix
 when you are repeatedly running similar commands but
 do not want to delete previous output.

 In addition to checking for valid AFNI prefix,
 the script will look for matching files with extensions:
    1D 1D.dset m nii asc ply 1D.coord 1D.topo coord topo srf

 Script is slow, it is for lazy people.