Of course, to say "<" ++ tag ++ ">" is very ugly, so you'd want to write it as angle tag. angle is a function? How is it implemented? In typical function programming style:

angle :: String -> String
angle s = surround "<" ">" s
{- This can, in "points free" style, be written:
angle = surround "<" ">"  -- look ma, no explicit variable!
 -}

surround :: String -> String -> String -> String
surround start end text = start ++ text ++ end

-- The idea is to reuse surround:
quote   = surround "'" "'"
bracket = surround "[" "]"
braces  = surround "{" "}"

... etc.
[download]

But this is straying off-topic for this site...