in reply to Re^4: Valid values of Tk::Text see() function.
in thread Valid values of Tk::Text see() function.

So, you want to ensure that the $linenumbers widget is positioned with the same vertical scroll as the $t widget. Perhaps you should ask $t where to scroll to: 
(my $ytop, undef) = $t->yview;
$linenumbers->yviewMoveto( $ytop );

[download]
(not tested)

Incidentally, how have you managed to display a number such as 950 in a 4-pixel wide widget?

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