$ perl -MData::Dumper -e"%h=(a=>{1..4},b=>{5..8});print Dumper\%h"
$VAR1 = {
          'a' => {
                   '1' => 2,
                   '3' => 4
                 },
          'b' => {
                   '7' => 8,
                   '5' => 6
                 }
        };