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

my %hash = (Matt => 24,
            Dana => 19,
            Eric => 28,
            Sara => 20,
            John => 17,
            Mike => 23,);

print Dumper \%hash;

my @sort = sort {$hash{$a} <=> $hash{$b}} keys %hash;
($hash{$sort[0]}, $hash{$sort[-1]})
     = ($hash{$sort[-1]}, $hash{$sort[0]});

print Dumper \%hash;