Not sure what your point is, but see also values and List::Util (if you don't need the intermediate array)...

use strict;
use warnings;
use List::Util qw(max);

my %hash = (1=>10,2=>20,3=>30,4=>40,5=>50);
my $max  = max(values %hash);
print "Max value was $max\n";

__END__

Max value was 50
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