I prefer using -textvariable as Rhose++ pointed out, but if you really want to use ->get(), it needs to happen AFTER something is put into the Entry. Try this:

my $name;
my $main = MainWindow->new();
$main->Label(-text=>"Company Name:")->pack();
my $entry = $main->Entry()->pack;
$entry->focus();
$main->Button(-text=>"Continue", -command=> sub {$name = $entry->get()
+; $main->destroy();})->pack();
$main->Button(-text=>"Cancel", -command => sub {exit})->pack();
$main->bind('<Return>' => sub {$main->destroy});
MainLoop;
die "$name";
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Also, next time, if you're going to include the error perl gave you, include all of the lines leading up to it. You can't have an error at line 38 of a 10 line script. . . :)