function try_subst
  # Use s/word/replacement<tab> to replace word with replacement 
  # in last command
  commandline | read -l saved_commandline

  set -l pattern '^s/..*/.*$'

  if commandline -t | grep -E -q "$pattern"
    commandline -tr (echo -n "$history[1]" | sed -e (commandline -t)/g)
  else
    commandline -f complete
  end
end