BEFORE   | AFTER  | COMMENT
-------------+--------+----------------
    '^(foo)' | BAR    | Regular use
   '\^(foo)' | ^(foo) | Escaped ^
   "\^(foo)" | BAR    | Perl squashes \^
             |        | in double quotes
  '\\^(foo)' | \^(foo)| Confused with '\BAR'?
  "\\^(foo)" | ^(foo) | Double quotes