my @a= qw( a b c   e  h j   l m n p       );
    my @b= qw(   b c d e f  j k l m     r s t );
    my @diff= easy( \@a, \@b );

##</code><code>##

  #         @a      @b        @a       @b
  # same?  range   range    values   values
  (   0,   0=>0,   0=>-1,  #    a  !
      1,   1=>2,   0=> 1,  #  b c  =  b c
      0,   3=>2,   2=> 2,  #       !  d
      1,   3=>3,   3=> 3,  #    e  =  e
      0,   4=>4,   4=> 4,  #    f  !  h
      1,   5=>5,   5=> 5,  #    j  =  j
      0,   6=>5,   6=> 6,  #       !  k
      1,   6=>7,   7=> 8,  #  l m  =  l m
      0,   8=>9,   9=>11,  #  n p  !  r s t
  );

##</code><code>##

    my @a= qw( a b c   e  h j   l m n p       );
    my @b= qw(   b c d e f  j k l m     r s t );
    my $diff= easy( \@a, \@b );
    while(  @$diff  ) {
        my( $same, $aMin, $aMax, $bMin, $bMax )=
            splice @$diff, 0, 5;
        my $a= join "", @a[$aMin..$aMax];
        if(  $same  ) {
            print $a;
        } else {
            print "<s>$a</s>"   if  "" ne $a;
            my $b= join "", @b[$bMin..$bMax];
            print "<b>$b</b>"   if  "" ne $b;
        }
    }

##</code><code>##

<s>a</s>bc<b>d</b>e<s>h</s><b>f</b>j<b>k</b>lm<s>np</s><b>rst</b>

##</code><code>##

    $_ .= $/   for  @a, @b;
    my $diff= easy( \@a, \@b );
    while(  @$diff  ) {
        my( $same, $aMin, $aMax, $bMin, $bMax )=
            splice @$diff, 0, 5;
        if(  $same  ) {
            for(  @a[$aMin..$aMax]  ) {
                print " $_";
            }
        } else {
            for(  @a[$aMin..$aMax]  ) {
                print "-$_";
            }
            for(  @b[$bMin..$bMax]  ) {
                print "+$_";
            }
        }
    }

##</code><code>##

-a
 b
 c
+d
 e
-h
+f
 j
+k
 l
 m
-n
-p
+r
+s
+t

##</code><code>##

    my $diff= easy( \@a, \@b );
    while(  @$diff  ) {
        my( $same, $aMin, $aMax, $bMin, $bMax )=
            splice @$diff, 0, 5;
        $_++   for  $aMin, $aMax, $bMin, $bMax;
        next   if  $same;
        my $sep= '';
        if(  $bMax < $bMin  ) {
            print "$aMin,$aMax","d$bMax\n";
        } elsif(  $aMax < $aMin  ) {
            print "$aMax","a$bMin,$bMax\n";
        } else {
            $sep= "---\n";
            print "$aMin,$aMax","c$bMin,$bMax\n";
        }
        for(  @a[$aMin-1..$aMax-1]  ) {
            print "< $_";
        }
        print $sep;
        for(  @b[$bMin-1..$bMax-1]  ) {
            print "> $_";
        }
    }

##</code><code>##

1,1d0
< a
3a3,3
> d
5,5c5,5
< h
---
> f
6a7,7
> k
9,10c10,12
< n
< p
---
> r
> s
> t

##</code><code>##

sub easy
{
    my $a= shift;      # array ref
    my $b= shift;      # array ref
    my @diff= ( 1, 0, -1, 0, -1 );
    traverse_sequences( $a, $b, {
        MATCH => sub {
            my( $aEnd, $bEnd )= @_;
            $_++ for my( $aTop, $bTop )= @diff[ 2-5, 4-5 ];
            if(  $aTop < $aEnd  ||  $bTop < $bEnd  ) {
                push @diff, 0, $aTop, $aEnd-1, $bTop, $bEnd-1,
                            1, $aEnd, $aEnd,   $bEnd, $bEnd;
            } else {
                @diff[ 2-5, 4-5 ]= ( $aEnd, $bEnd );
            }
        },
    }, @_ );
    my( $aEnd, $bEnd )= ( 0+@$a, 0+@$b );
    $_++ for my( $aTop, $bTop )= @diff[ 2-5, 4-5 ];
    if(  $aTop < $aEnd  ||  $bTop < $bEnd  ) {
        push @diff, 0, $aTop, $aEnd-1, $bTop, $bEnd-1;
    }
    splice @diff, 0, 5   if  $diff[2] < 0  &&  $diff[4] < 0;
    return wantarray ? @diff : \@diff;
}