$word = quotemeta($word);

     quotemeta EXPR
     quotemeta
             Returns the value of EXPR with all non-"word"
             characters backslashed.  (That is, all characters
             not matching "/[A-Za-z_0-9]/" will be preceded by a
             backslash in the returned string, regardless of any
             locale settings.)  This is the internal function
             implementing the "\Q" escape in double-quoted
             strings.

             If EXPR is omitted, uses $_.