This is quickshot and can surely be optimized

my @elems = qw(x y z);
my @is    = qw(foo) x 10;
my @new   = ();

my $i = 0;
my $j = 0;
my $k = int(@is / @elems)-1;

for ( $j=0; $j<@is; $j++ )
{
    push @new, $is[$j] . $elems[$i];
    
    $i++ if $j % int(@is / @elems) == $k and $i+1<@elems;
}

print "@new";
[download]

Update: Too late as always ;-)