use strict;
use warnings;
use feature 'say';
use List::Util qw/ min pairmap /;
use List::MoreUtils qw/ slide /;

say
    min
    slide { $b - $a }
    sort  { $a <=> $b }
    map   { $_, $_ + 60 * 24 }
    pairmap { 60 * $a + $b }
    map   /(\d\d):(\d\d)/,
    @$_
    for 
        [ qw/ 00:00 23:55 20:00 /],
        [ qw/ 01:01 00:50 00:57 /],
        [ qw/ 10:10 09:30 09:00 09:55 /]
;