#!/usr/bin/perl
use strict;
use warnings;
my %hash=(1=>10,2=>20,3=>30,4=>40,5=>50);


my $max=0;
my @out=map{
    $_=$hash{$_};
    if($_>$max){$max=$_} else { ()}
#    $_;
}keys %hash;

print "Max value was $max\n";
use Data::Dumper; print Dumper \@out;

# prints
Max value was 50
$VAR1 = [
          40,
          50
        ];