43.2. Data Values in PL/Perl
  The argument values supplied to a PL/Perl function's code are
   simply the input arguments converted to text form (just as if they
   had been displayed by a
  
   SELECT
  
  statement).
   Conversely, the
  
   return
  
  and
  
   return_next
  
  commands will accept any string that is acceptable input format
   for the function's declared return type.
 
  If this behavior is inconvenient for a particular case, it can be
   improved by using a transform, as already illustrated
   for
  
   bool
  
  values.  Several examples of transform modules
   are included in the
  
   PostgreSQL
  
  distribution.