Erlang's two most important features are finding their way into many languages:<p>- Message passing with mailboxes and pattern matching receive statements<p>- Supervision trees, allowing the separation of function code and error handling
I hate quoting myself but:<p>Any sufficiently complicated concurrent program in another language contains an ad hoc informally-specified bug-ridden slow implementation of half of Erlang.<p>With all respect to Greenspun.