...
<form method="post" action="$ENV{'SCRIPT_NAME'}?action=add_2&Month=$selected_month&Year=$selected_year">
<table align="center" border="0" cellpadding="1" cellspacing="0" width="100%">
~;
	print qq~<tr>\n~;
	@data = (PTG1, PTG2, PTG3, PTG4, F1, F2, F3, F4, R1, R2, R3, R4, JS1, JM2, JL3, JX4);
	foreach $key(@data) {
		print qq~<td><b>$key</b></td>\n~;
	}
	print qq~</tr>
<tr>
~;
	foreach $key(@data) {
		print qq~<td>
<select name="$key" size="13" multiple>
<option value="-1" selected></option>
~;
		$days_in_this_month = $days_in_month[$input{'Month'}];
		if ( $input{'Month'} == 2  and leap_year($input{'Year'})) { $days_in_this_month = 29; }
		for ($i=1; $i<=$days_in_this_month; $i++) {
			print qq~<option value="$i">$i</option>\n~;
        	}
		print qq~</select>
</td>
~;
	}
	print qq~</tr>
</table>
<center>
<input type="submit" name="submit"> 
<input type="reset">
</center>
</form>
...