Am I entering a world of pain...

...by trying to port a SQL Server application to Postgresql?

I am unable to get a simple function to work.  Any ideas as to what is wrong 
with it?

create or replace function droptable (varchar(255)) returns void as '
begin
  drop table $1;
  return;
end;
' language 'plpgsql';

This is what happens when I execute the function:

select droptable('asdfadsfasfd');
WARNING:  Error occurred while executing PL/pgSQL function droptable
WARNING:  line 2 at SQL statement
ERROR:  parser: parse error at or near "$1" at character 13

Regards

AM