Some further data points. It also SEGVs at the same point when running in the debugger under Linux with Perl 5.12.4 and Tk 804.029 and under Linux with Perl 5.14.2 and Tk 804.030.

Even more trimmed down example:

use Tk; 
my $m = MainWindow->new;
my $t = $m->Text->pack;
$t->search('-regexp', '', '1.0', 'end'); # debugger crash
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