Alternative:

use strict;
use warnings;
use feature qw( say );

use DateTime::Format::Strptime qw( );

my $strp = DateTime::Format::Strptime->new(
   pattern   => "%T %b %d %Y",
   locale    => "en",
   time_zone => "local",
   on_error  => "croak",
);

my $year = "2011";

my $ownTime  = $strp->parse_datetime("11:00:44 Aug 31"." ".$year);
my $waitTime = $strp->parse_datetime("11:03:44 Aug 31"." ".$year);
my $dur = $waitTime->delta_ms($ownTime);
say $dur->minutes();
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DateTime::Format::Strptime, DateTime, DateTime::Duration