Then why didn't you say so in the first place?

Instead of printing, just collect all your data into the string:

my $info;
foreach (sort keys %hoh){
    my $data = "$_ ";
    my $tmp_hash = $hoh{$_};
    foreach (sort keys %$tmp_hash){
        $data .= $$tmp_hash{$_} . " ";
    }
    $info .= $data . "\n";
}

print "$info"; # here you would append that to your mail body
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