Help for this page
>perl -le "for ('a'..'z') { $h{$_}=1; print scalar %h } 1/8 ... 24/32 25/32 26/32
>perl -le "for ('a'..'z') { $h{$_ x 2}=1; print scalar %h } 1/8 ... 21/32 21/32 21/32