Is there a way more easy to write this code?

#!/usr/bin/perl

use strict;
use warnings;

foreach my $char1 ('', 'a'..'z', 'A'..'Z', '_' ) {
    foreach my $char2 ('', 'a'..'z', 'A'..'Z', '_' ) {
        foreach my $char3 ('', 'a'..'z', 'A'..'Z', '_' ) {
            foreach my $char4 ('', 'a'..'z', 'A'..'Z', '_' ) {
                foreach my $char5 ('', 'a'..'z', 'A'..'Z', '_' ) {
                    foreach my $char6 ('', 'a'..'z', 'A'..'Z', '_' ) {
                        my $plain = $char1 . $char2 . $char3 . $char4 
+. $char5. $char6;
                        print $plain,"\n";
                    }
                }
            }
        }
    }
}
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I have tried Regexp::Genex but it seem not for me because the output are only a few $plain.

#!/usr/bin/perl

use warnings;
use strict;
use Regexp::Genex qw(:all);

my $regex = '\w{1,6}';

for my $plain ( strings($regex) ) {
    print $plain, "\n";
}
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