#!/usr/bin/perl

use strict ;
use warnings ;

my $st= 'a' x 100000 ;     # this program runs as O(n^2)
utf8::upgrade($st) ;       # ... when operating on a string with the utf8 flag set

while (1) {
    $st=~ /\G(?=a)/gc ;
    pos($st)= pos($st) ;   # without this, there's an early exit next line
    last unless $st=~ /\G(?=a)/gc ;
    $st=~ /\Ga/gc ;        # increments pos()
}

print "done\n" ;