It shouldn't be hard to adapt the answers found in Categorized Questions and Answers >> QandASection: dates and times >> How do I find the difference in days between two dates, in a cool perl way? to hours.

use DateTime;
use DateTime::Format::Strptime;

my $now = DateTime->now;

my $parser = DateTime::Format::Strptime->new(
    pattern => '%b %d %H:%M',
);
my $date = $parser->parse_datetime( 'Jan 30 14:21' );

my $diff = $now - $date;

# This is required to convert to seconds as per DateTime documentation
+.
my $seconds_diff = $now->clone->add_duration($diff)
                              ->subtract_datetime_absolute($now);
my $hours_diff = int( $seconds / 60 );
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