Because Gleam compiles to Erlang, it can seamlessly integrate with the larger BEAM ecosystem, including existing Erlang and Elixir OTP applications and librarie

Because Gleam compiles to Erlang, it can seamlessly integrate with the larger BEAM ecosystem, including existing Erlang and Elixir OTP applications and libraries. @external decorator: This escape hatch allows Gleam code to call functions defined in Erlang or Elixir modules. While it bypasses Gleam's type checks for the function call, it provides a powerful way to leverage the full capabilities of the existing OTP ecosystem. I believe the biggest reason it's hard to replicate OTP fully and quickly is Gleam's type system (but I could be wrong).