use Algorithm::Diff qw(traverse_sequences);

#----------------------------------------------------------------------------------
#				C O M P A R A T O R
#----------------------------------------------------------------------------------

sub comparator {
my $str1 = shift @_;
my $str2 = shift @_;
my $original = '';
my $revised  = '';

my @from = split(/([ ,.:;"?!-])/, $str1);
my @to   = split(/([ ,.:;"?!-])/, $str2);

my $OS = q|<span class="m">|;
my $OE = q|</span>|;
my $RS = q|<span class="m">|;
my $RE = q|</span>|;

  traverse_sequences( \@from, \@to,
    {
    MATCH     => sub { 
    	my $oldtext = $from[shift()]; 
    	 if ($oldtext =~ /<P>/) {
    		$original .= "</p>\n<p>";
    		$revised  .= "</p>\n<p>"
    	 } else {
    		$original .= "$oldtext"; 
    		$revised .= "$oldtext" 
    	 }
    	},
    DISCARD_A => sub { 
    	 my $oldtext = $from[shift()]; 
    	 if ($oldtext =~ /<P>/) {
    		$original .= "</p>\n<p>"
    	 } elsif ($original =~ m!</span>\s$!) {
    	 	if ($oldtext =~ m/(?:[,.:;"?!-])/) {
    	 		$original =~ s/(?:<\/span>)*\s+$/$oldtext$OE/;    	 		
    	 	} else {
    	 		$original =~ s/<\/span>\s$/ $oldtext$OE/;
    	 	}
    	 } else {
        	$original .= $OS.$oldtext.$OE 
    	 }
    	},
    DISCARD_B => sub { 
    	my $newtext = $to[pop()];     
    	 if ($newtext =~ /<P>/) {
    		$revised .= "</p>\n<p>"
    	 } elsif ($revised =~ m!</span>\s$!) {
    	 	if ($newtext =~ m/(?:[,.:;"?!-])/) {
	    	 	$revised =~ s/(?:<\/span>)*\s+$/$newtext$RE/;
    	 	} else {
	    	 	$revised =~ s/<\/span>\s$/ $newtext$RE/;
	    	 }
    	 } else {
    	 	$revised  .= $RS.$newtext.$RE 
    	 }
    	},
    } );
    
    $original =~ s~^(</p>)(.*+)$~$2$1~;
    $revised  =~ s~^(</p>)(.*+)$~$2$1~;
    
	return ($original, $revised);
	
} #END SUB comparator