You have to adjust your data structure AND the template:

use strict;
use warnings;
use Data::Dumper;
use HTML::Template;

my %hash = (
    ABC => "john",
    DEF => "mike",
    GHI => "mary",
);

my $tmpl = HTML::Template->new(scalarref => \q{
<table>
    <thead>
        <tr><TMPL_LOOP TH>
            <th><TMPL_VAR CELL></th></TMPL_LOOP>
        </tr>
    </thead>
    <tbody><TMPL_LOOP TD>
        <tr>
            <td><TMPL_VAR KEY></td>
            <td><TMPL_VAR VAL></td>
        </tr></TMPL_LOOP>
    </tbody>
</table>
});

$tmpl->param(
    TH => [ map { CELL => $_ }, qw( Type Value ) ],
    TD => [ map { KEY => $_, VAL => $hash{$_} }, keys %hash ],
);

print $tmpl->output;
[download]

Output:

<table>
    <thead>
        <tr>
            <th>Type</th>
            <th>Value</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>ABC</td>
            <td>john</td>
        </tr>
        <tr>
            <td>DEF</td>
            <td>mike</td>
        </tr>
        <tr>
            <td>GHI</td>
            <td>mary</td>
        </tr>
    </tbody>
</table>
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)