#!/usr/bin/perl
 
use strict;
my (%hash, %large_data_structure_hash, @arr);
 
# fill hash and array
foreach ( qw/i1 i2 i3 i4 i5 i6 i7 i8 i9 i10/ ) {
    $hash{$_} = #data structure with lots of info;
    push @arr, $_;   #array used for random key selection
}
 
#randomly select a few item from hash and get its data
foreach(1 .. 4) {
    my $random_element = $arr[ rand @arr ];  #randomly select key 
    my %large_data_structure_hash = %{ $hash{$random_element} };
 
    #do whatever I want with %large_data_structure_hash
}
 
exit;