Of course, List::Util also comes with max() and maxstr():

#!perl

use 5.010;
use strict;
use warnings;
no warnings 'numeric';
# otherwise max() gives a warning on keys "a" and "b"

my %hash = (a => 'value' , b => 'value', 0 => 'value', 1 => 'value');
# the values don't matter for this example

use List::Util (qw/max maxstr/);
my $max    = max (keys %hash);
my $maxstr = maxstr (keys %hash);
say "numeric: $max\tstring: $maxstr";
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returns

numeric: 1    string: b
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