# perl -slw
use strict;
use re 'eval';
use Data::Dumper;

use vars qw[%Config];          # A global hash to contain the data

my $re_pair = qr{                  # key=value [[#;]comment text\n]
	(?{ our ($key, $value, $comment)=() })             # local vars

	(\w+) (?{ $key = $^N })            # Capture & save the keyname
	=
	(\w+) (?{ $value = $^N })            # Capture & save the value
	(?:
		\s+                                 # obligatory whitespace
		[#;]                      # oblig. comment card - either or
		([^\n]+) (?{ $comment = $^N }) # Capture & save the comment
		\n
	)?                                                # zero or one
	\s*

	      # If we got here, we have key/name comment?, so save them
	(?{ $Config{$section}{$key} = [ $value, $comment ] })
}x;

my $re_section = qr{                     # consist of [label] pairs*
	(?{ our ($section)=undef })	            # Init the section label

	[[] ([^]]+) []]                              # Capture the label

	                       # Save it. Create a key to hold the pairs
	(?{ $section = $^N; $Config{$section} = undef })

	            # zero or more pair sounded by optional while space.
	\s* $re_pair* \s*
}x;

my $re_file =  qr{           # A file consists of 1 or more sections
	$re_section+
}x;

my $data = do{ local $/; <DATA> } . $/;             # slurp the file

$data =~ m[$re_file];                                     # parse it

print Dumper \%Config;                                      # Use it

__DATA__
[Section1]
key1=value1
key2=value2	#comment
key3=value3

[Section2]
key4=value4
key5=value5	;Comment2

[Section3]