anchor.diff:  
   C======================================================================C
   
  -      SUBROUTINE gcmdln(ifile,ofile,nvar,seed)
  +      SUBROUTINE gcmdln(ifile,ofile,nvar,seed,p)
         IMPLICIT NONE
         CHARACTER*80 ifile,ofile,tag
  -      INTEGER i,narg,nvar,seed
  +      INTEGER i,narg,nvar,seed,p
         ifile = 'none'
         ofile = 'none'
         seed = -1
         nvar = 1
  +      p    = 0
         narg = iargc()
         if (narg.eq.0) call usage('')
         i = 0
  
positive.code: C----
        IMPLICIT none
        CHARACTER*80 ifile,ofile
        INTEGER i,nvar,input,output,idum,seed
        REAL*8 val(10),dval(10)
        EXTERNAL ran2
        REAL ran2,random
  
  C Parse command line
        call gcmdln(ifile,ofile,nvar,seed)
        if (ifile.eq.'stdin') then
            input = 5
        else
            input = 11
            open(unit=input,file=ifile,status='old')
        endif
        if (ofile.eq.'print'.or.ofile.eq.'stdout') then
            output = 6
        else
            output = 12
  
negative.code:           write(*,*)
        endif
        write(*,*)
       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)'
  