#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %base = (xx => [{ls => 'ls xx 2>&1'},
                   {ps => 'ps xx 2>&1'},
                   ],
            yy => [{top    => 'top yy 2>&1'},
                   {finger => 'finger yy 2>&1'},
                   ],
            );

my %output;
for my $key (keys %base) {
    for my $element (@{$base{$key}}) {
        my $inner_key = (keys %$element)[0];
        my $command = (values %$element)[0];
        my $result = `$command`;
        push @{$output{$key}}, $result;
    }
}

print Dumper \%output;