use Algorithm::Permute;

my @patterns = ();

my $p = new Algorithm::Permute(['X', 'Y', 'Z']);
while (@res = $p->next) {
    push @patterns, join('', @res);
}

my $pattern = join '|', @patterns;

print "$pattern\n";

# give the pattern a test...
while (<DATA>) {
    chomp;
    print "$_ is ", /^(?:$pattern)$/ ? 'good' : 'bad', "\n";
}

__DATA__
XYX
XYZ
ZYY
ZXY
ZYX
XXYZ

##</code><code>##

ZYX|YZX|YXZ|ZXY|XZY|XYZ

XYX is bad
XYZ is good
ZYY is bad
ZXY is good
ZYX is good
XXYZ is bad