An optimisation for you using map:

Replace the following

my @loop_data = ();
my @keys = ();
my @values = ();

# incidentally, the "my %hash" on the next line should be just "%hash"

while ((my $key, my $value) = each my %hash) {
  push(@keys, $key);
  push(@values, $value);
}

while (@keys and @values) {
  my %row_data;
  
  $row_data{KEY} = shift @keys;
  $row_data{VALUE} = shift @values;

  push(@loop_data, \%row_data);
}
[download]

with...

my @loop_data = map { { KEY => $_, VALUE => $hash{$_} } } keys %hash;
[download]

map is a way to build lists from lists. in this case you can use it to iterate through the keys of %hash and create a hashref for each key/value pair to be stored in @loop_data.

Don't be confused by the { { ... } } syntax though - map likes a block (i.e. map { ... } list) or a single expression (i.e. map expression, list - notice the comma) but since you want hashrefs ({})we have to use a block or it will get confused when you put a comma after. Maybe I just confused you even more - RTFM and you should see what I mean.

Hope this helps.

Update

Regarding your actual question I think if you put the loop inside the <table></table> around the rows then it'll all be in the same table - is that what you were asking? Sorry, I'm feeling a bit thick today!

<table width=400 border=1 cellspacing=0 cellpadding=0>
  <TMPL_UNLESS SHOW_ALL_LOOP>
  <tr>
    <td>
      Nothing to see here folks, move along!
    </td>
  </tr>
  </TMPL_UNLESS>
  <TMPL_LOOP SHOW_ALL_LOOP>
  <tr>
    <td valign=top bgcolor=#dddddd>
      <b>Key</b>:&nbsp;<TMPL_VAR NAME="KEY">
      <b>Value</b>:&nbsp;<TMPL_VAR NAME="VALUE">
    </td>
  </tr>
  </TMPL_LOOP>
</table><br>
[download]

Update 2

Check out DB_File::Lock for obvious reasons.

Update 3

For your second question you could just put the template vars in separate table cells:

    <td valign=top bgcolor=#dddddd>
      <b>Key</b>:&nbsp;<TMPL_VAR NAME="KEY">
    </td>
    <td>
      <b>Value</b>:&nbsp;<TMPL_VAR NAME="VALUE">
    </td>
[download]

   larryk                                          
perl -le "s,,reverse killer,e,y,rifle,lycra,,print"