[ic] recursive perl subroutine

[John Allman]

hi - i'm trying to trace through a reasonably shallow category tree to 
find if a product fits into a particular category. i want a function to 
return 0 if the products category, or it's category's category etc is 
equal to the WCODE variable defined in catalog.cfg and 0 otherwise (0 
being the root node of the tree).

the function below is an effort to do that. if i try calling 
checktree(0) it returns 1 as requested and if i try calling 
checktree(200) it returns 0 (the value of WCODE is 200). so far so good.

if i try checktree(201) it doesn't seem to return anything. the entry in 
cattable with code 201 has pcode 200. checktree should recursively pass 
the value of pcode until it hits 200 or 0 (it is guaranteed to hit one 
or the other) i have gotten it to return $pcode instead of 
checktree($pcode) and it returns 200 which is correct. but it doesn't 
seem to like passing $pcode back into itself.

error.log contains no errors. checktree is defined inside a [perl] block 
  in a page.

the tree looks something like this
			0
			|
		-----------------
		|		|
		200		other numbers
		|
	-----------------
	|		|
	201		other numbers

code is the identifier for the node and pcode is the identifier for its 
parent node.

sub checktree {
                         my ($catcode)=@_;
                         if($catcode == 0)
                         {
                                 return 1;
                         }
                         elsif($catcode == $Variable->{WCODE})
                         {
                                 return 0;
                         }
                         else
                         {
                                 $db = $Db{cattable};
                                 $sql = "select pcode from cattable 
where pcode=".$catcode;
                                 $parent = $db ->query({sql => "select 
pcode from cattable where code=".$catcode});
                                 $row = shift (@$parent);
                                 ($pcode) = @$row;
                                 return checktree($pcode);
                         }
}

is there something built into interchange to stop recursive calls? or is 
there a syntax error in my code (i in no way claim to be a perl expert)?

thanks in advance!

John