As mentioned laready, your code looks fine.. just wanted to toss in a couple comments...

• When working with Date::Calc, I find it much easier and clearer to use arrays for the year/month/day or year/month/day/hour/min/sec sets.
  * To facilitate this, note the change in return value for getMeanTime() in the code below.
• Those multiple sprintf's should really just be a single one and just take advantage of sprintf's template nature, and the print sprintf is redundant (should just be a printf).
• note that gmtime() is the same as gmtime(time).
• note from the Date::Calc docs for Delta_YMDHMS: "Arguments are expected to be in chronological order to yield a (usually) positive result."

so i would write it something like:

use Date::Calc qw(Delta_YMDHMS);

# @d arrays are (y,mon,d,h,min,s)
my @dt1 = getMeanTime();
sleep(2);
my @dt2 = getMeanTime();
my @dt = Delta_YMDHMS( @dt1, @dt2 );
printf "%02d/%02d/%04d %02d:$02d:$02d", @dt[2,1,0, 3..5];

sub getMeanTime {
  my @t = gmtime;
  return ( $t[5]+1900, $t[4]+1, $t[3], @t[2..0] );  # (y, mon, day, h,
+ min, s)
}
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Also note that instead of gmtime, you can (just for ease of the array usage and for Date::Clac consistency) use Today_and_Now():

use Date::Calc qw(Delta_YMDHMS Today_and_Now);

# @d arrays are (y,mon,d,h,min,s)
my @dt1 = Today_and_Now();
sleep(2);
my @dt2 = Today_and_Now();
my @dt = Delta_YMDHMS( @dt1, @dt2 );
printf "%02d/%02d/%04d %02d:$02d:$02d", @dt[2,1,0, 3..5];
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