Here's something to try out:

$file = shift or die "Need a file name!\n";

@closedtags = qw(hmtl head body b i u);
@opentags = qw(a img);
open(HTMLFILE, "$file") || die "Could not open $file: $!\n";
undef $/;
$html=<HTMLFILE>;
close(HTMLFILE);

## The magic part:
while($html =~ m#<(/?)([^ >]*)[^>]*>#gi) {
  if ($1) { $tag{lc $2}--; }
  else    { $tag{lc $2}++; }
}

## Now we have lots of options to play with:


## Show ALL tags, matched then unmatched:
print "Matched tags:\n";
for $x (sort keys %tag) { print "$x\n" unless $tag{$x}; }
print "Unmatched tags:\n";
for $x (sort keys %tag) { print "$x\n" if $tag{$x}; }

## Go through our list of 'closed' and check each:
for $x (@closedtags) {
  printf "Results for html tag %5s: ", $x;
  if (defined $tag{$x}) {
    print $tag{$x} ? "NOT balanced\n" : "balanced\n";
  }
  else { print "None found.\n"; }
}

# Etc. The regexp does a fairly good job, but 
# misses weird cases like > embedded in quotes, etc.
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