[io grant] Improve code example
[io grant] Improve code example

- remove Perl 5-ist parentheses
- avoid repetition of a variable
- fix incorrect Range (prose says "first three files")
- gather IO::Paths, not strings
- Don't use regex when we don't need it
- No need to test .f
dmaestro/doc,stmuk/doc,MasterDuke17/doc,jonathanstowe/doc,perl6/doc,jonathanstowe/doc,perl6/doc,stmuk/doc,dmaestro/doc,gfldex/doc,stmuk/doc,MasterDuke17/doc,tbrowder/doc,tbrowder/doc,antquinonez/doc,perl6/doc,MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,stmuk/doc,gfldex/doc,antquinonez/doc,tbrowder/doc,tbrowder/doc,antquinonez/doc,gfldex/doc,dmaestro/doc,dmaestro/doc,antquinonez/doc,perl6/doc,gfldex/doc,jonathanstowe/doc,MasterDuke17/doc,perl6/doc,stmuk/doc,antquinonez/doc,gfldex/doc,jonathanstowe/doc