Documentation for infix => assembled from the following pages:

Language documentation: Operators §

From Operators

(Operators) infix => §

sub infix:«=>»($key, Mu $value --> Pair:D)

Pair constructor.

Constructs a Pair object with the left-hand side as the key and the right-hand side as the value.

Note that the => operator is syntactically special-cased, in that it allows unquoted identifier on the left-hand side.

my $p = a => 1;
say $p.key;         # OUTPUT: «a␤» 
say $p.value;       # OUTPUT: «1␤»

A Pair within an argument list with an unquoted identifier on the left is interpreted as a named argument.

See the Terms language documentation for more ways to create Pair objects.