[f-nsp] as-path acl and prepending occurrences

[Marcus Eide]

Hi,
Because of the AS47868 (SuproNet) ~250 times as-path prepending issue, I
want to limit my customers announced as-path occurrence (prepending) to
some number by using curly brackets and specifying number of occurrences. 
E.g "ip as-path access-list as-cust-in permit ^(65000_){1-10}$" to limit 1
to 10 occurrences of as 65000.

But the 4.0 IronWare in my XMR complains about the syntax:

telnet at r1(config)#ip as-path access-list as-cust-in seq 1 permit
^(65000_){1-10}$              
{ not supported, use \{
grammar failure
telnet at r1(config)#

Is it okay to escape the curly brackets or should I use another syntax?

Regards
/Marcus