Something like this?

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

use Tk;
my $mw = MainWindow->new(-title => "Tk");
my $f = $mw->Frame->pack;

# 1
$f->Text()->pack(-side => 'left')->focus;

my $b = $mw->Button(-text => 'Submit',
                    -command => sub {print "Submitted\n"},
                   )->pack;
# 2
$mw->bind('<Return>', [sub { $b->invoke; Tk->break; }]);

# 3
my $g1;
$f->Radiobutton(-text => 'Option1',
                 -value => 1,
                 -variable => \$g1)->pack;
$f->Radiobutton(-text => 'Option2',
                 -value => 2,
                 -variable => \$g1)->pack->select;
$f->Radiobutton(-text => 'Option3',
                 -value => 3,
                 -variable => \$g1)->pack;

MainLoop();
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