I was using your code and found a problem with different duration parameters.
my $first = "01:25:52:421";
my $last = "01:26:29:369";
For this example the seconds and milliseconds in the $last
variable have lesser amounts than in the $first
The program hangs and will not complete. It only executes the first two print statements. The result should be 00:00:36:948
I don't know what can be done to get the program to run to completion (and execute the third print).
I've been working on this for several days, reading the docs for DateTime::Format::Duration and can't find the answer there - maybe I don't understand it well.