The standard line-draw algorithm (as far as I can remember) can be used here:

my @elems = ("x", "y", "z");
# array size may be varied (lesser or more than 3)
my @tobepopulated = ("foo", "foo", "foo", "foo", "foo", "foo", "foo", 
++"foo", "foo", "foo");
# this can be more 10 elements 

my $m= 2 * scalar @tobepopulated;
my $d= 2 * scalar @elems;
die "too few elements to be populated" unless $m >= $d;

my $i= 0;
my $n= $d/2;

foreach (@tobepopulated) {
    $_.= '-' . $elems[$i];
    $n+= $d;
    if ( $n > $m ) {
        $n-= $m;
        ++$i;
    }
}
print join "\n",@tobepopulated,'';
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