my $entry = $frame ->
  Entry ( -justify=>'left', -relief=>'sunken', -textvariable=>\$entry_var ,
         -validate        => "key",
         -validatecommand => sub {$_[1] =~ /[a-zA-Z_-]/},
         -invalidcommand  => sub {print "bitte nur Buchstaben eingeben";},
         -width=>12, -state=>'normal' ) ->
  pack(-anchor=>'w', -side=>'left');