Mnemonics

"list"

• creates list
• and also a general parenthesiser

Used as a brace pair or quote pair

() creates "capture literal"

Operators containing this character

\() creates a Capture literal wrapped in a scalar
|() creates a Capture literal and then flattens it
:() creates a Signature object and is used in closure parameters

As an adverb

() can be used as a parenthesizer in adverbs

Old, deprecated, or other language uses

() used to be considered a list constructor but is more strictly a capture now.