my $days_re = join('|', @days);
$days_re = qr/$days_re/;

##</code><code>##

my @days    = qw( Sun Mon Tue Wed Thu Fri Sat ); 
my $days_re = re_alternative(map {qr/\Q$_\E/} @days);

##</code><code>##

my @days    = qw( Sun Mon Tue Wed Thu Fri Sat );
my $days_re = join("|", map {qr/\Q$_\E/} @days);
   $days_re = qr($days_re);

##</code><code>##

--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/
map{y/X_/\n /;print}map{pop@$_}@/for@/