use strict;

my @letters = ("a" .. "z");
my @ziffern = (1..9, 0, "a" .. "z");

$anzahl = 100;
$wortlaenge = 7;

for (1..$anzahl) {
   my $wort;
   for $i (1..$wortlaenge) {
        if ($i < 4) {
            $wort .= $letters[rand 27];
        } else {
            $wort .= $ziffern[rand 37];
        }
    }
    print  $wort . "\n";
}