From language/operators

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multi sub infix:<xx>()
multi sub infix:<xx>(Mu \x)
multi sub infix:<xx>(&x, Num:D() $n)
multi sub infix:<xx>(&x, Whatever)
multi sub infix:<xx>(&x, Bool:D $b)
multi sub infix:<xx>(&x, Int:D $n)
multi sub infix:<xx>(Mu \x, Num:D() $n)
multi sub infix:<xx>(Mu \x, Whatever)
multi sub infix:<xx>(Mu \x, Bool:D $b)
multi sub infix:<xx>(Mu \x, Int:D $n)

List repetition operator

In general, it returns a Sequence of $a repeated and evaluated $b times ($b is coerced to Int). If $b <= 0 , the empty list is returned. It will return an error with no operand, and return the operand itself with a single operand. An exception X::Numeric::CannotConvert will be thrown if $b is -Inf or NaN.

The left-hand side is evaluated for each repetition, so

say [1, 2] xx 5;
# OUTPUT: «([1 2] [1 2] [1 2] [1 2] [1 2])␤»

returns five distinct arrays (but with the same content each time), and

rand xx 3

returns three pseudo random numbers that are determined independently.

The right-hand side can be *, in which case a lazy, infinite list is returned. If it's a Bool, a Seq with a single element is returned if it's True.