Improve the example
Improve the example

To reflect what is indicated by @lizmat here
https://stackoverflow.com/questions/41531393/can-i-use-a-standalone-signature-as-a-signature-in-perl-6#comment84619436_41543023
and also reflect the intent of putting signatures into variables, as
said in #1748 (by myself, but still). Also modifies the example
changed in #1777, so thanks to @jimav for drawing this to our attention.

antquinonez/doc,stmuk/doc,dmaestro/doc,stmuk/doc,dmaestro/doc,jonathanstowe/doc,stmuk/doc,jonathanstowe/doc,tbrowder/doc,perl6/doc,dmaestro/doc,tbrowder/doc,MasterDuke17/doc,jonathanstowe/doc,antquinonez/doc,perl6/doc,MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,antquinonez/doc,perl6/doc,dmaestro/doc,perl6/doc,MasterDuke17/doc,antquinonez/doc,stmuk/doc,perl6/doc,antquinonez/doc,MasterDuke17/doc,stmuk/doc,tbrowder/doc,jonathanstowe/doc,tbrowder/doc