It depends what you mean by even, I am assuming even offsets 0,2,4,6, etc.:

my @all = qw(zero wun two tree fower fife six seven ait niner);
my @evens = @all[grep {not $_ % 2} 0..$#all];
[download]

However I rather like:

my @evens = keys %{{@all}};
[download]

but (being a hash) the items must be unique, and you loose the original order. If the other values are required (offsets 1,3,5,7) then use values instead of keys.
Update: removed some superfluous parentheses and changed not, if you see what I mean.