Documentation for infix (==), infix ≡ assembled from the following pages:

Language documentation: Operators §

From Operators

(Operators) infix (==), infix ≡ §

multi sub infix:<(==)>($a,$b --> Bool:D)

Set equality operator.

Returns True if $a and $b are identical.

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

Language documentation: Sets, bags, and mixes §

From Sets, bags, and mixes

(Sets, bags, and mixes) infix (==), infix ≡ §

Returns True if $a and $b are identical, else False. More information, Wikipedia definition.