@[] is syntax for a "seq", which is similar to a C++ vector, ArrayList in Java/C#, or a python list. It's a heap-allocated array that automatically resizes. In

@[] is syntax for a "seq", which is similar to a C++ vector, ArrayList in Java/C#, or a python list. It's a heap-allocated array that automatically resizes. In contrast with [], which is mostly identical to a C array: fixed size and lives on the stack.