my ($sec,$min,$hour,@garbage) = gmtime(time - $^T);
my $runningtime = sprintf("%02d:%02d:%02d", $hour, $min, $sec);
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actual time at this valuation minus the special Perl VAR holding the scripts invocation time gives back $runningtime as a string "hh:mm:ss"
I know, it's quick and dirty and not good enough for benchmarking, but to give you something to compare :-)
Have a nice day
All decision is left to your taste