G'day rinaldi,

Welcome to the monastery.

The questions in your node title and content differ.

"print every nth element of an array."

Here's one way to print every nth element:

$ perl -Mstrict -Mwarnings -e '
    my @array = "a" .. "z";
    my $n = 10;
    print $array[$_] for grep { ! (($_ + 1) % $n) } 0 .. $#array;
'
jt
[download]

"print '\n' every nth element of an @array"

Here's how you might print a newline after every nth element (I'm assuming that's what meant unless you really did want to just print a string of newlines and nothing else):

$ perl -Mstrict -Mwarnings -e '
    my @array = "a" .. "z";
    my $n = 10;
    print map { $array[$_] . (($_ + 1) % $n ? "" : "\n") } 0 .. $#arra
+y;
'
abcdefghij
klmnopqrst
uvwxyz
[download]