### HEADING OF RECORD 1 ####
Logical device ID=08E1
LINE_THAT_DOES_NOT_BOTHER_ME
ANOTHER_LINE_THAT_DOES_NOT_BOTHER_ME
29 8/0/2/1/0.18.152.0.0.6.1  c29t6d1   FA  5eA
30 8/0/3/1/0.17.152.0.0.6.1  c30t6d1   FA 12e
31 8/0/8/1/0.17.150.0.0.6.1  c31t6d1   FA 10eA
32 8/0/9/1/0.18.150.0.0.6.1  c32t6d1   FA 11eA

### HEADING OF RECORD 2 ####
Logical device ID=08E2
LINE_THAT_DOES_NOT_BOTHER_ME
ANOTHER_LINE_THAT_DOES_NOT_BOTHER_ME
29 8/0/2/1/0.18.152.0.0.4.1  c29t4d1   FA  5eA
30 8/0/3/1/0.17.152.0.0.4.1  c30t4d1   FA 12eA
31 8/0/8/1/0.17.150.0.0.4.1  c31t4d1   FA 10eA
32 8/0/9/1/0.18.150.0.0.4.1  c32t4d1   FA 11eA

### HEADING OF RECORD 3 ####
(...)

##</code><code>##

%hash = (
'08E1' => ['c29t6d1','c30t6d1','c31t6d1','c32t6d1'],
'08E2' => ['c29t4d1','c30t4d1','c31t41','c32t4d1'],
(...)
)

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

my %hash;
open ( FH, "powermt display dev=all|");# data stream comes from here

$/ = '';
while (<FH>) {
    my ($id) = ( $_ =~ /Logical device ID=(\w+)/ );
    push (@{$hash{$id}}, $1) if /(c\d+t\d+d\d+)/;
}

print Dumper (\%hash);

##</code><code>##

$VAR1 = {
          '08E1' => [
                      'c29t6d1'
                    ],
          '08E2' => [
                      'c29t4d1'
                    ],
(...)