4.3BSD-UWisc/lib/learn/editor/L41.1a

#print
One thing you must be careful of is that the substitute command does not
know about word boundaries.  It will change the first occurrence of a
letter string it matches without regard to blanks or punctuation around it.
Thus, if the current line is
   i would rather be the king
and you type
   s/the/a/p
you get
   i would raar be the king
instead of
   i would rather be a king
Right?  You should always print lines after changing them to avoid
missing such errors.  You can defend against them by increasing the
amount of context you specify; in this case, for example, you could say
   s/the /a /p
and get
   i would rather be a king
Often the "$" operator is useful here, if you want to change the last
thing on the line.  In the file 'text', the third line reads
   never, never, never, never, never
Edit this file to make the third line read
  never, never, never, never, or hardly ever
Rewrite the file and type "ready".
#create Ref
why should a dog, a horse, a rat, have life,
and thou no breath at all? thou'lt come no more,
never, never, never, never, or hardly ever
pray you, undo this button.  thank you, sir.
#create text
why should a dog, a horse, a rat, have life,
and thou no breath at all? thou'lt come no more,
never, never, never, never, never
pray you, undo this button.  thank you, sir.
#user
#cmp text Ref
#log
#next
42.1a 10
41.1b 5
42.2a 6