When the all operator appears before an event template, when that event template finds a match, it continues to watch for subsequent events that also match the template.

Consider the following event expression:

This event listener would match on every A and the first B that follows it. The way this works is that upon encountering an A, the correlator creates a second event listener to seek the next A. Both event listeners would be active concurrently; one looking for a B to successfully match the sequence specified, the other initially looking for an A. If more As are encountered the procedure is repeated; this behavior continues until either the monitor or the event listener are explicitly killed.

Consider the following sequence of incoming events:

With these input events, on all A() -> B() would return the following:

{A1, B1}, {A2, B1} and {A3, B3}.

Note that all is a unary operator and has higher precedence than ->, or and and.