Excellent suggestion to use Date::Calc. Here's one way to implement it with your data:

use Modern::Perl;
use Date::Calc qw/Delta_YMDHMS/;

# From the documentation:
# Delta_YMDHMS
#      ($D_y,$D_m,$D_d, $Dh,$Dm,$Ds) =
#      Delta_YMDHMS($year1,$month1,$day1, $hour1,$min1,$sec1,
#                   $year2,$month2,$day2, $hour2,$min2,$sec2);
#

my $start = '2012-08-08 17:14:22';
my $end   = '2012-08-10 17:14:22';

my @start = $start =~ /(\d+)/g;
my @end   = $end   =~ /(\d+)/g;

my ( $D_y, $D_m, $D_d, $Dh, $Dm, $Ds ) = Delta_YMDHMS( @start, @end );

say "The difference between $start and $end is:\nYears: $D_y, Months: 
+$D_m, Days: $D_d, Hours: $Dh, Minutes: $Dm, Seconds: $Ds";
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Output:

The difference between 2012-08-08 17:14:22 and 2012-08-10 17:14:22 is:
Years: 0, Months: 0, Days: 2, Hours: 0, Minutes: 0, Seconds: 0
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Hope this helps!