If I undestand you (and with some handwaving), this should work:

#furiously waving hand!
my %fields = get_fields(); # field name => old value

my @fields;
for(keys %fields )
{
  push @fields, { fname => $_, fvalue => $fields{$_} };
}

my $tmpl = HTML::Template->new();
$tmpl->params( old_fields => \@fields );
print $tmpl->output;
[download]

Then in your template code:

<tmpl_loop name='old_fields'>
  <input type='text' name='<tmpl_var fname>' value='<tmpl_var fvalue>'
</tmpl_loop>
[download]

You probably want to use escape=html in the tmpl tags, but i've omitted them for the sake of brevity.