In this case I think that an XML::Parser call wrapped in an eval is your best bet. Something like this:

foreach (@list_of_20_000_files) {
  my $p = XML::Parser->new;
  eval { $p->parsefile($_) };
  if ($@) {
    print "$_ is bad\n";
  } else {
    print "$_ is good\n";
  }
}
[download]

The one thing that worries me tho' is that you talk about 'snippets' of well-formed XML. If those snippets don't have one enclosing element, then they won't be well-formed.

--
<http://www.dave.org.uk>

"Perl makes the fun jobs fun
and the boring jobs bearable" - me