=begin pod

=TITLE class X::Syntax::Signature::InvocantMarker

    class X::Syntax::Signature::InvocantMarker does X::Syntax { }

Syntax error when the invocant in a signature is anywhere else than after the
first parameter.

For example

    :($a, $b: $c)

dies with

    ===SORRY!===
    Can only use : as invocant marker in a signature after the first parameter

See also: L<Signature>.

=end pod