Documentation for routine placeholder

Documentation for routine placeholder, assembled from the following types:

class X::Placeholder::Block

From X::Placeholder::Block

(X::Placeholder::Block) method placeholder

Returns the name of the (first) illegally used placeholder.

class X::Signature::Placeholder

From X::Signature::Placeholder

(X::Signature::Placeholder) method placeholder

method placeholder(--> Str:D)

Returns the name of a placeholder that was used in a block that already had a signature.