my $string = "a(b)cd(e)f"; 
my @parts = split /(?=.{5}$)/, $string';

##</code><code>##

local $_ = "a(b)cd(e)f"; 
my @parts = split /.{5}/g;

##</code><code>##

local $_ = "a(b)cd(e)f"; 
my @parts = /.{5}/g;