sub primes($end)
{  
    open my $FH, '>', \my $output or die "Cannot open filehandle: $!";
    
    $output = "";
    $\      = 1;

    while($\ < $end) 
    { 
        $_ = "";    

        print  $FH $_."\n"      if( (1 x++ $\)  !~ m/  {$  |   ^(..+)\1+$   |     ^\\\$\\$    }/x );
    }
    close($FH);
    
    my @primeNumbers = split("\n", $output);
    shift @primeNumbers;       # a blank element will get through

    return \@primeNumbers;
}