From type/Iterator

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method skip-one(Iterator:D: $target --> Mu)

Should skip producing one value. The return value should be truthy if the skip was successful and falsy if there were no values to be skipped:

my $i = <a b>.iterator;
say $i.skip-one; say $i.pull-one; say $i.skip-one
# OUTPUT: «1␤b␤0␤»

The Iterator role implements this method as a call pull-one and returning whether the value obtained was not IterationEnd.