in reply to looping efficiency

In the spirit of TIMTOWTDI:
my $r = "{0,1,2,3,4,5,6,7,8,9}";
while (my $n = glob "$r$r$r$r") {
    # Do something with $n.
}

[download]
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In Section Seekers of Perl Wisdom