Performance is different, and return hash ref has a much better performance. Try the following test: (I tried 1000 by 200, return hash cost 20 secs, when return ref only cost 13 secs. Well... you can see how slow my PC is.)

use strict;

sub return_hash {
    my %hash;

    for (0..shift) {
        $hash{$_} = $_;
    }
    return %hash;
}

sub return_hash_ref {
    my %hash;
    for (0..shift) {
        $hash{$_} = $_;
    }
    return \%hash;
}

my $ti = time();
for (0..$ARGV[1]) {
    my %hash = return_hash($ARGV[0]);
}
print "return hash takes: ", time() - $ti, " secs\n";
$ti = time();
for (0..$ARGV[1]) {
    my $hash = return_hash_ref($ARGV[0]);
}
print "return hash REF takes: ", time() - $ti, " secs\n";
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