use strict;
use warnings;

use autodie;

use Data::Dumper;

my $filename = '11123126_1.dat';  # could take this from command line

# ignore blank or # comment lines
use constant IGNORE => qr{ ^ \s* (?: [#] .* )? $ }xms;

my $rx_identifier = qr{ \w+ }xms;
my $rx_toplevel   = qr{ $rx_identifier }xms;
my $rx_key        = qr{ $rx_identifier }xms;
my $rx_value      = qr{ $rx_identifier }xms;

my $toplevel;
my %hash;

open my $fh, '<', $filename;

RECORD:
while (my $record = <$fh>) {

    next RECORD if $record =~ IGNORE;
  # print Dumper $record;  # for debug

    my $got_toplevel =
    my ($tl) =
    $record =~ m{ ^ \s* ($rx_toplevel) \s* : \s* $ }xms;

    $toplevel = $tl, next RECORD if $got_toplevel;
  # print Dumper $toplevel;  # for debug

    my $got_key_val =
    my ($key, $value) =
    $record =~ m{ ^ \s* ($rx_key) \s* : \s* ($rx_value) \s* $ }xms;
  # print Dumper $key, $value;  # for debug

    die "no top level seen" unless defined $toplevel;
    $hash{$toplevel}{$key} = $value, next RECORD if $got_key_val;

    # no valid record seen.
    die "bad record '$record'";

    }  # end while RECORD

print Dumper \%hash;

close $fh;

exit;

# subroutines ######################################################

# none for now