You need to pass the callback and its arguments in an array reference as follows, where the first argument is a ref to the callback, followed by the subroutine arguments themselves: 
$widget->Button(-text=>"mybutton", -command=> [ \&mysub, 'a1', 'a2' ])

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There's a nice section on this in Mastering Perl/TK.

In reply to Re: Subs attached to Tk Buttons by Mr_Jon
in thread Subs attached to Tk Buttons by Scarborough

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