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Uncaught exception from user code:
Can't call method "Button" on an undefined value at C:\Documents and S
+ettings\Eoin\Desktop\calc.pl line 52.

for my $i (
qw/
   7 8 9 * n*
   4 5 6 - \
   1 2 3 + =
   0 . C     / )

my $mw = new MainWindow(-title => 'Calc');
$mw->geometry("300x300");
...
}

MainLoop;