• Erlang

[case Elem of "foo" -> "bar"; _ -> Elem end || Elem <- X].

• Clojure

(replace {"foo" "bar"} x)

• C++

std::replace(x.begin(), x.end(), "foo", "bar");

• C#

int i;
while ((i = x.IndexOf("foo")) != -1)
    x[i] = "bar";

• Dart

for (var i = 0; i < x.length; i++) {
  if (x[i] == 'foo') x[i] = 'bar';
}

• Dart

x = x.map((e) => e == 'foo' ? 'bar' : e).toList();

• Fortran

  where (x == "foo")
     x = "bar"
  endwhere

• Go

func replaceAll[T comparable](s []T, old, new T) {
	for i, v := range s {
		if v == old {
			s[i] = new
		}
	}
}

replaceAll(x, "foo", "bar")

• Go

for i, v := range x {
	if v == "foo" {
		x[i] = "bar"
	}
}

• Haskell

replaced = map (\e -> if e == "foo" then "bar" else e) x

• JS

x = x.map(e => e === 'foo' ? 'bar' : e);

• Java

ListIterator<String> i = x.listIterator();
while (i.hasNext())
    if (i.next().equals("foo")) i.set("bar");

• Java

x.replaceAll(e -> e.equals("foo") ? "bar" : e);

• Java

x = x.stream()
     .map(s -> s.equals("foo") ? "bar" : s)
     .toList();

• Pascal

for i := 0 to x.count - 1 do
  if x[i] = 'foo' then
    x[i] := 'bar';

• Perl

map { s/^foo$/bar/g } @x;

• Python

for i, v in enumerate(x):
  if v == "foo":
    x[i] = "bar"

• Python

x = ["bar" if v=="foo" else v for v in x]

• Python

for i, v in enumerate(x):
    if v == 'foo': x[i] = 'bar'

• Ruby

x.map!{|el| el == "foo" ? "bar" : el}

• Rust

for v in &mut x {
    if *v == "foo" {
        *v = "bar";
    }
}