use Tk;
use strict;

my $mw = MainWindow->new();
my $b = $mw->Button(-text=>"Click me",-command=>sub{foo()})->pack();

MainLoop;

sub foo {
  my $fname = $mw->getOpenFile(-initialdir=>"/tmp",-title=>"trying");
  return unless defined ($fname);
  print "You've selected $fname\n";
}