#!/usr/local/bin/perl
#!/usr/bin/perl
use strict;
use warnings;
my $max = shift || 100;
my @primes;

sieve:
for my $ns ( map { 1 x $_ } ( 2 .. $max ) ) {
    for my $ds (@primes) {
        last if $ds x length($ds) gt $ns;
        next sieve if $ns =~ /^(?:$ds)+$/;
    }
    push @primes, $ns;
    printf "%3d:%s\n", length $ns, $ns;
}