my $label_Rxp=$leftframe2->Label(
  -textvariable => \$Rxpackets_text,
  -anchor =>'e',
  -relief => 'groove')
->pack(-fill => 'both');
.............
$Rxpackets_text=`/sbin/ifconfig ppp0 |grep "RX packets"|cut -d ":" -f 2 |cut -d " " -f 1`;