my $text = 'this {{}}should be {{test {{ab{{c}}d}} zzzz}}good {{bw}}';

my $nested = 100;
my $re = '{{(?:[^{}]+|';
$re   .= $re    x ($nested);
$re   .= ')*}}' x ($nested + 1);
$text =~ s/$re//sg;

print "$text\n";

__END__|OUTPUT:
this should be good