Tk has had a problem, in programatically trying to set strings into the handy mouse clipboard. Tk::Clipboard didn't work as it should. Then when you tried to copy from a text box with selectAll, a nasty newline would always be added. Very crude. I found by methodical hacking attempts, how to strip the newline.
#!/usr/bin/perl
use warnings;
use strict;
use Tk;
# a "phantom newline"-free copy'n'paste to
# the mouse clipboard
my $mw = tkinit;
my $textbox = $mw->Text(); #never packed
$mw->Button(-text =>'CLipAppend',
-command=>sub{
$textbox->clipboardClear;
$textbox->delete('1.0','end');
$textbox->insert('end','foobarz');
$textbox->selectAll;
#this next line must come after the selectAll
$textbox->delete('end - 1 chars','end');
$textbox->clipboardColumnCopy;
print chr(07); #beep
})->pack();
MainLoop;