$ ./1.strftime.pl 
Argument "Sun Dec  1 00:29:42 2019" isn't numeric in subtraction (-) at ./1.strftime.pl line 9.
Argument "Sun Dec  1 00:29:52 2019" isn't numeric in subtraction (-) at ./1.strftime.pl line 9.
It took me 0 seconds
Usage: POSIX::strftime(fmt, sec, min, hour, mday, mon, year, wday = -1, yday = -1, isdst = -1) at ./1.strftime.pl line 11.
$ cat 1.strftime.pl 
#!/usr/bin/perl

use strict;    
use warnings;
use POSIX qw(strftime);
my $start = gmtime();
sleep 10;
my $end = gmtime();
my $duration = $end - $start;
print "It took me $duration seconds\n";
my $start_date = strftime "%Y-%m-%d %H:%M:%S", $start;
my $end_date = strftime "%Y-%m-%d %H:%M:%S", $end;
print "I was started on $start_date and ended on $end_date\n";

$