Text.Regex  regex-posix does NOT support 
    word boundary
    Use package: Text.RE.TDFA.String instead
    
    Text.Regex.Posix and Text.Regex.Posix.String wraps the C POSIX-2 Regex API.

    It does not support multiple bytes char (unicode).
    Use Text.Regex.TDFA and Text.Regex.TDFA.Text instead.

    -- /Users/cat/myfile/bitbucket/haskell/regexExample.hs 

    > :m -Text.Regex.Posix
    > :m +Text.Regex.TDFA
    > :m +Text.Regex.TDFA.Text
    > st = "iabbr vodiv: ⨸"
    > splitRegex (mkRegex ":") st
    ["iabbr vodiv"," \10808"]
    >

    --{-# LANGUAGE QuasiQuotes #-}
    --import Text.RE.TDFA.String
    main = do 
        -- replace word boundary, replace one, and replace all
        let s1 = "mydog dog dog (dog)" ?=~/ [ed|${adr}(\):?///< div class="dog">${adr}< /div> |]
        let s2 = "mydog dog dog (dog)" *=~/ [ed|${adr}(\):?///< div class="dog">${adr}< /div> |]
        putStrLn $ "replace one: =>[" ++ s1 ++ "]"
        putStrLn $ "replace all: =>[" ++ s2 ++ "]"

    re1 = "my food"         =~ "foo"::Bool                      -- True
    re2 = "my food foo"     =~ "foo"::String                    -- "foo"
    re3 = "my foolish fool" =~ "foo."::[[String]]               -- [["fool"],["fool"]]
    re4 = "my foolish fool" =~ "foo."::(String, String, String) -- ("my ","fool","ish fool")

    -- word boundary, search word and replace
    let s = "mydog dog-- dog pig cat dog fox"
    searchReplace s word "[\\0]"

    let r1 = mkRegex "google"
    let input = "http://google.com"
    let replace1 = "[\\0]"
    putStrLn $ subRegex r1 input replace1            -- http://[google].com

    let r3 = mkRegex "(na)+"
    putStrLn $ subRegex r3 "banana" "[\\0] {\\1}"

    let r5 = mkRegex ".*\\.pdf"
    putStrLn $ subRegex r5 "http://file.pdf" "[\\0]" -- [http://file.PDF]

    -- capture group, capture email address
    
    let rgx = mkRegex "([A-Za-z._-]+)+@(([a-z])+\\.([a-z]{2,4}))"
         ↑
         + - - - - - - - +          Input Str                    whole str  fst group     snd group
                         ↓             ↓                             ↓           ↓            ↓
    putStrLn $ subRegex rgx "root_admin.last-name@gmail.com"   "7. [\\0]       {\\1}        {\\2}"

    let r7 = mkRegexWithOpts "(.*\\.pdf)" True False
    let input = "/home/user/file/mybook.PDF"
    let callMeMaybe = matchRegex r7 input

    let r7 = mkRegexWithOpts "(\\.pdf)" True False
    let input = "/home/user/file/mybook.PDF"
    let callMeMaybe = matchRegex r7 input

    -- capture phone number
    let p1 = mkRegex "[0-9]{3}[ -]?[0-9]{3}[ -]?[0-9]{4}" 
    -- replace string
    putStrLn $ subRegex p1 "779-123-4483"  "[\\0]"    -- [416-123-4483]

    -- split Regex
    print $ splitRegex(mkRegex ":") "PaloAlto:MountainView" -- ["PaloAlto","MountainView"]

    -- split Regex, ERROR: illegal byte sequence
    print $ splitRegex(mkRegex ":") "iabbr vRightarrow ⟹ "

    -- capture function in ObjectiveC
    let me = mkRegex "(-|\\+)[[:space:]]*\\([[:space:]]*[[:print:]]+[[:space:]]*\\)[[:space:]]*[[:graph:]]+\
    \[[:space:]]*:?[[:space:]]*([[:space:]]*[[:graph:]]+[[:space:]]*:[[:space:]]*[[:graph:]]+[[:space:]]*)*"

    putStrLn $ subRegex me "- (NSstring*) swap :" "[\\0]" -- [- (NSstring*) swap :]

    putStrLn $ subRegex me "- (NSstring*) method:(Integer)num width:(Integer)width\ 
    \ height:(NSString*)str" "12. [\\0]"
    -- [- (NSstring*) method:(Integer)num width:(Integer)width  height:(NSString*)str]

    let r7 = mkRegex "([A-Za-z]+)" 
    let count = matchCount r7 "haskell java C++ ObejctiveC aa#" 
    putStrLn $ "count = " ++ show count

    let r8 = mkRegex "[a-z]+"
    let bo = matchTest r8 "22323"
    putStrLn $ "Is matched = " ++ show bo -- return True