use strict;
use Tk;
use Tk::LabFrame;

my $mw = MainWindow->new;

my $lf = $mw->LabFrame(
   -labelside => 'acrosstop',
   -label => "My Form"
)->pack(qw/-padx 10 -pady 5/);

my $inFrame = $lf->Frame->
   pack(qw/-padx 10 -pady 5/);

$inFrame->Label(-text => "Field A: ")->grid(
   $inFrame->Entry(-width => 20), -pady => 2);

$inFrame->Label(-text => "Field B: ")->grid(
   $inFrame->Entry(-width => 20), -pady => 2);

$mw->Button(
   -text => "Submit",
   -command => \&Submit
)->pack(-pady => 4);

$mw->bind('<Key-Return>', \&Submit);

MainLoop;

sub Submit {
   print "form submitted\n";
}