$maindata = $mwmidfr->Columns('-columnlabels' 	=> \@headers,
			                  '-listforeground'   => 'black',
				    		  '-listbackground'   => 'tan',
				    		  '-buttonbackground' => 'red',
				    		  '-buttonforeground' => 'yellow',
				    		  '-selectmode'	   => 'extended',
							  '-selectcommand'	=> \&modify,
				    		  '-zoom' 			=> '1',
							  '-sortcommand'	  => '$a cmp $b',
							  '-sort'		     => 'true')->pack();

$maindata->configure(0, '-sortcommand' => '$a <=> $b');