elixir_string_match

example.esx

# assign the prefix to a variable
iex(1)> pre = "he"
"he"

# a string match against the prefix works as expected
iex(2)> << "he", rest::binary >> = "hello"
"hello"

# a string match using the pinned prefix variable doesn't
iex(3)> << ^pre, rest::binary >> = "hello"
** (MatchError) no match of right hand side value: "hello"


# why?