Now the problem is here:

   -command => &numpress($i))
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The thing being assigned to the "-command" attribute needs to be an anonymous subroutine, a reference to a named subroutine, or else a reference to an array whose elements are: named_subroutine_ref, arg1(, arg2 ...) -- in other words, either of the following would be the right way to do what you want:

   -command => sub { numpress( $i ) }
# or
   -command => [ \&numpress, $i ]
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The way you had it written, your subroutine is actually being called when the Button is being created, and Perl/Tk is trying to use the return value of the sub as the value for "-command" -- not good.