Problem 9 -- grep matches
  two or more deed                    "deed.*deed"
  end with deed                       "deed$"
  i, o, and u at least once           "i.*o.*u|i.*u.*o|o.*i.*u|o.*u.*i|u.*i.*o|u.*o.*i"
  exactly two e                       "^[^e]*e[^e]*e[^e]*$"
There were also a few submissions involving Perl regular expressions
PS: Technically, these Perl extensions really aren't regular
PS: Backreferences aren't useful for these examples


Problem 11 -- find

  file names ends in .s                               -type f -name "*.s" -print
  file name ends in .s and modified 1000 days ago     -type f -mtime +1000 -name "*.s" -print
  file name ends in .c and file contains Stoplight    -type f -name "*.c" -exec grep -q "Stoplight" {} \; -print
Note in last one, it is the file and not the file name that contains Stoplight