Add another ｢is pure｣ example
Add another ｢is pure｣ example

Hopefully resolves #1231.

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