use v6;

my Str $sep = "x";
my Str $buf = q{abcxdefx1};

"No class:".say;
.say for $buf.split(rx{ $sep }, :all).map(~*);

class Foo {
    has Str $.sep is rw = 'x';

    method p (Str $b) {
	my Str $s = $!sep;

	"Class with copy".say;
	for $b.split(rx{ $s }, :all).map(~*) {
	    .say;
	    }

	"Class direct".say;
	for $b.split(rx{ $!sep }, :all).map(~*) {
	    .say;
	    }
	}
    }

Foo.new.p($buf);

=>

No class:
abc
x
def
x
1
Class with copy
abc
x
def
x
1
Class direct
abcxdefx1