use DateTime::Duration;
                                                                                
my $time1 = '11:30:25';
my $time2 = '12:45:40';
                                                                                
my ( $h1,$m1,$s1 ) = split /:/, $time1;
my ( $h2,$m2,$s2 ) = split /:/, $time2;
                                                                                
my $d1 = DateTime::Duration->new(hours => $h1, minutes => $m1, seconds => $s1);
my $d2 = DateTime::Duration->new(hours => $h2, minutes => $m2, seconds => $s2);
                                                                                
my $diff = $d2 - $d1;
                                                                                
print +join ':',$diff->in_units('hours','minutes','seconds');