Yet another time calculation in Perl

This is specifically for a delegate I am teaching right now. If I understand the requirements correctly, we hae two times in HH:MM:SS format and we wish to calculate the difference. I know, what if the times are on different days? No answer was given to that one, so I have assumed they are on the same day (today, to be exact).
This will probably change because the specification is a bit "wooly".

#!/usr/bin/perl

use strict;
use warnings;
use Time::Local;

sub str2time
{
   my $in = shift;
   my ($hour, $min, $sec) = split (/:/, $in);
   my ($mday,$mon,$year) = (localtime(time))[3,4,5];
   my $retn;
 
   # timelocal throws an exception on an invalid date/time
   eval {
      $retn = timelocal($sec,$min,$hour,$mday,$mon,$year);
   };
 
   return $retn;   # undef on error
}

print "Please enter the first time in HH:MM:SS format: ";
my $intime = <STDIN>;
chomp $intime;

my $time1 = str2time($intime);

die "Invalid time: $intime\n" if !defined $time1;
  
print "Please enter the 2nd   time in HH:MM:SS format: ";
$intime = <STDIN>;
chomp $intime;

my $time2 = str2time($intime);

die "Invalid time: $intime\n" if !defined $time1;


my $diff;
if ( $time1 > $time2 ) {
    $diff = $time1 - $time2
}
else {
    $diff = $time2 - $time1
}

my $mins  = int($diff / 60);
my $hours = int($mins / 60);
$mins     = $mins - ($hours * 60);
my $secs  = $diff - ($mins  * 60);

printf "Difference: %02d:%02d:%02d\n", $hours,$mins,$secs;