use CGI;
my $c = CGI->new();

my %hash = qw/data and stuff/; #however you fill the hash


#Step 1
my @keys = sort keys %hash; # this should maintain the same order, assuming hash doesn't change

#Step 2
my $counter = $c->param('page');


#step 3
my $begin = $counter * $items_per_page;
my $end = $begin + $items_per_page;


#step 4
print @hash{ @keys[ $begin..$end ] }; #deep voodoo