...decrease memory usage while processing a big XML files.

But you seem to be building a tree in memory that would then be quite big too. So either I am missing something, or you gave us too little information to really help you.

Thanks for you attention! You are right, I gave you too little information to help solving my problem. But at that time my handlers were absolutely "crude" and could not give the helpful information. I solved this problem. My handlers are below.

sub start_document {
    my $self = shift;
    $self->{lists} = [];
    $self->{curlist} = $self->{tree} = [];
}


#
#
sub start_element {
    my $self = shift;
    my $element = shift;
    my $name = $element->{Name};
    $self->{elem_name} = $element->{Name};
    
    my $id; my $var;
    if ($element->{Attributes}) {
        $id = $element->{Attributes}->{'{}id'}->{Value};
        $var = $element->{Attributes}->{'{}var'}->{Value};
    }
    
    if ($name eq 'part') {
        my $newlist = [ {id=>$id, var=>$var} ];
       
        push @{ $self->{lists} }, $self->{curlist};
        if ($is_parent) {
            push @{$self->{curlist}[0]{childs}}, @{$newlist};
        } else {
            push @{ $self->{curlist} }, @{$newlist};
        }
        $self->{curlist} = $newlist;        
    }
    
    $is_parent++ if $element->{Name} eq 'part';
}


#
#
sub end_element {
    my $self = shift;
    my $element = shift;
    my $name = $element->{Name};
    
    # Save template name;
    if ($name eq 'template') {
        $self->{template} = $self->{char};
    }

    if ($name eq 'part') {
        $self->{curlist} = pop @{ $self->{lists} }; 
        $is_parent--;
    }
}


#
#
sub characters {
    my $self = shift;
    my $chars = shift;
    my $text  = $chars->{Data};
    my $clist = $self->{curlist};
    $self->{char} = codes2chars($text);
}


#
#
sub end_document {
    my $self = shift;

    delete ($self->{curlist});
    delete ($self->{lists});

    my $tree = $self->{tree};
    delete ($self->{tree});
    $struct->{$self->{menu_name}}->{parts} = $tree;
    $struct->{$self->{menu_name}}->{template} = $self->{template};
}
[download]