Select Code to Download

my @b = @{ reduce { push @$a, $b if !@$a || $b ne $a->[-1]; $a } [], @
+a };

my @b = list_reduce { push @$_, $b if !@$_ || $b ne $_->[-1]; undef } 
+undef, @a;

...
my @b = list_reduce { push @$_, $b if defined($b) && $b ne $a; $b } un
+def, @a;

my @b = list_reduce { push @$_, grep defined && $_ ne $a, $b; $b } und
+ef, @a;