#!/usr/bin/perl --
use strict;
use warnings;
use XML::LibXML;
use Tk;

my $xpc;

my $mw = MainWindow->new( -title => 'GUI' );
$mw->Button(
    -text => 'Load XML',
    -command => [ \&tk_Load_Export , \$xpc ],
)->grid(-column => '0', -row => '0', -sticky => 'e');
MainLoop;

sub tk_Load_Export {
    my( $ref_xpc ) = @_;
#~     my $filename = $mw->getOpenFile( -title => 'Load XML', -defaultextension => '.xml', -initialdir => '.' ) or return;
    my $filename = 'C:\bigbigxml.xml';
    import_XML( $filename , $ref_xpc );
}

sub import_XML {
    my( $filename , $ref_xpc ) = @_;
    print "Reading the XML file $filename\n\n";
    undef $$xpc; # free previous $dom
    my $dom = XML::LibXML->load_xml(location => $filename, huge => 1);
    $$xpc = XML::LibXML::XPathContext->new($dom);
    print "XML imported\n"; 
}