moveto => 1 works if you do it after the geometry manager has run, which seems to be the trick for both of your problems.

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1213368

use strict;
use warnings;
use Tk;
use Tk::Pane;

my $mw = MainWindow->new( );
$mw->minsize(200,300);

my $pane = $mw->Scrolled( 'Pane',
    -scrollbars => 'e',
    -border => 2,
    )->pack(-fill=>'both', -expand=>1);

foreach my $x (1..100) {
    my $label = $pane->Label(
        -text    => $x,
    )->pack(-side=>'top', -fill=>'x', -expand=>0);
}
$mw->after(1, sub { $pane->yview(moveto => 1) } );
MainLoop;
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