$ != $[]

[rayozzie]

In try.jsonata.org, the following evaluate identically as a way of demoting the entire source object into a field.

{
"event":$[0]
}

...and...

{
"event":$[]
}

...are equivalent to...

{
"event":$
}

In jsonata-go, $[0] does what one would expect, but the others do not.