#!perl
use strict;

my $text = join '|',qw(DOCTYPE html meta header);
my $re = qr/$text/;

my $filename = 'd:/perl/test.xhtml';
my $tidy = '..../tidy/bin/tidy.exe'; # change to your path
my @msg = qx"$tidy -eq -utf8 $filename 2>&1";

for (@msg){
  print $_ unless /$re/;
}

# line 10 column 1 - Warning: missing </section>