#!/usr/bin/perl
use strict; use warnings;

use Parse::RecDescent;

$::RD_TRACE = 1;

my $grammar = q{
    <autotree>
    program : statement
            | block

    statement : IDENT IDENT ';'

    block : IDENT '{' program '}'

    IDENT : /[A-J]+/
};

my $parser = Parse::RecDescent->new( $grammar );
my $input  = join '', <DATA>;

my $tree   = $parser->program( $input );

use Data::Dumper; warn Dumper( $tree );

__DATA__

ABC {
    DEF {
        GHI ABD;
    }
}