You can replace \b<something> with (?<=^|\s)<something> and <something>\b with <something>(?=$|\s). These are called assertions, the first is a positive lookbehind assertion, the second is a positive lookahead. Look them up in man.txt. To match, for example, "blah" or "bleh" only as separate words you'd use
(?<=^|\s)bl[ae]h(?=$|\s)
Regarding m/pattern/, m allows you to set the quote character. By default, the quotes (ie the pair of characters than encloses the actual pattern) are /..../. With m, you can use any other char. For example, here:
mi^rc$i
the actual pattern is ^rc$, the i's play the role of /.
