#!/usr/bin/perl -w
use strict;

my $hash_ref= {1002=>[1,2,3,4,5],
               1001=>[6,7,8,9,10],
               3   =>[2]};
               
print_HoL($hash_ref);

sub print_HoL
{
   my $rHoL = shift;
   foreach my $key (keys %$rHoL) 
   {
      print "$key: @{$rHoL->{$key}}\n"; 
   }
}
__END__
Prints:
1001: 6 7 8 9 10
1002: 1 2 3 4 5
3: 2