In Operators§

See primary documentation in context for infix ∌

multi sub infix:<>($a,$b --> Bool:D)

Non-membership operator.

Returns True if $a does not contain $b. Equivalent to !(cont).

say (1,2,3 4;       # OUTPUT: «True␤» 
say (1,2,3!(cont) 2# OUTPUT: «False␤» 

In Sets, bags, and mixes§

See primary documentation in context for infix ∌

Returns True if $a does not contain $b, else False. More information, Wikipedia definition.