The erl program starts an Erlang runtime system. The exact details (for example, whether erl is a script or a program and which other programs it calls) are system-dependent. commandline session $erl Erlang R15B01 (erts-5.9.1) [source] [64-bit] [async-threads:0] [kernel-poll:false] Eshell V5.9.1 (abort with ^G) 1> b(). ok 2> double = fun(value) -> 2*value end. ** …