- foreach original file
  - $linenum = 1;
  - while not eof
    - append the line to file "line${linenum}.dat"
    - $linenum++;
  - end
- end
- foreach line file
  - Compare num of lines returned by
    'cat line###.dat | sort | uniq'
    with the number of lines in line###.dat.
    If they're different, there are duplicate records.
- end