#!/usr/bin/perl

use strict;
use warnings;

undef $/;

my @blocks = map { [ split /\n/ ] }
    ( split /(?=ITEM)/, ( map { s/#.*\n//; $_ } <DATA> )[0] );

print "$_\n" for @{ $blocks[1] };    # print block no. 2

__DATA__
#This is the ITEM file
ITEM NO:1
[aaa]
111
[bbb]
222
[ccc]
333
ITEM NO:2
[ddd]
444
[eee]
555
[fff]
666
ITEM NO:3