anchor.diff:            write(*,*)
         endif
         write(*,*)
  -     1 'Usage: perturb -f IFILE -o OFILE -n NVAR [-seed SEED]'
  +     1 'Usage: perturb -f IFILE -o OFILE -n NVAR [-seed SEED] [-p]'
         write(*,*)
         write(*,*)
        1 '-f IFILE    Input data file with uncertainties (v1..vn d1..dn)'
  
positive.code:           elseif (tag(1:2).eq.'-f') then
                i = i + 1
                call getarg(i,ifile)
            elseif (tag(1:2).eq.'-h') then
                call usage('')
            else
  
negative.code:      1 '-seed SEED  Start random numbers with integer SEED ',
       2                  '(useful for continuing chain of rands)'
        write(*,*)
       1 '-p          Print results to standard output'
        write(*,*)
       1 '-h          Online help'
        write(*,*)
        STOP
  