Thanks a lot apl

Here is the program to take into account your remarks. However, there is still a problem. 

#! perl -slw
use strict;
use diagnostics;
use Data::Dump qw[ pp ];

sub by_hour{
    my ($a,$b) = @_;
    my $h_a;
    my $mn_a;
    my $h_b;
    my $mn_b;
    
    my $res;
    
    if ($a =~ /(\d\d):(\d\d)/){
            $h_a = $1;
            $mn_a = $2;
        }
    if ($b =~ /(\d\d):(\d\d)/){
            $h_a = $1;
            $mn_a = $2;
        }
    if ($h_a < $h_b){
        $res =    -1;
        }
    if ($h_a > $h_b){
        $res = 1;
        }
    if ($h_a == $h_b){
        
        if ($mn_a < $mn_b){
        $res = -1;
        }
        if ($mn_a > $mn_b){
        $res =1;
        }
        if ($mn_a == $mn_b){
        $res =    0;
        }
    }
    return $res;    
}

my %in;

while (<DATA>){
m[(\d\d:\d\d) (.+)$] and push @{ $in{ $1 } }, $2;
}

my @keys = keys %in;
my @times = sort @keys;

for my $hr ( sort by_hour keys %in ) {
    print STDOUT "$hr\n";
}


__DATA__
11:10 A1
12:30 E4
11:30 Z4
15:50 H5
12:02 H6
12:25 B2
11:25 A8
12:30 F3
14:30 E7
12:50 E15
12:55 E16

[download]

In reply to Re^2: sub routine to sort per time by steph_bow
in thread sub routine to sort per time by steph_bow

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