my $in  = 'bad.html';
my $out = 'tidied.html';
my $err = 'tidy.err';
my $cnf = 'tidy.cnf';

system( 
  'tidy.exe',
  '-asxml',
  -config => $cnf,
  -file   => $err,
  -output => $out,
  $in,
);