• PHP

$s = "This string 
is spanning
three lines";

• PHP

$s = <<<EOD
Huey
Dewey
Louie
EOD;

• JS

let s = "This is a very long string which needs \n" +
        "to wrap across multiple lines because \n" +
        "otherwise my code is unreadable.";

• JS

let s = "This is a very long string which needs \
to wrap across multiple lines because \
otherwise my code is unreadable.";

• JS

let s = `This is a very long string which needs 
to wrap across multiple lines because 
otherwise my code is unreadable.`;

• Ada

s : String := "Will this compile? " &
     "Oh yes it will";

• C

char *s = "Huey\n"
          "Dewey\n"
          "Louie";

• Clojure

(def s "Murs, ville,
Et port,
Asile
De mort,
Mer grise
Où brise
La brise,
Tout dort.")

• Cobol

IDENTIFICATION DIVISION.
PROGRAM-ID. multi-line string.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 s    PIC X(20).
01 str  PIC X(5) VALUE 'COBOL'.
01 str1 PIC X(4) VALUE 'RULE'.
01 str2 PIC X(3) VALUE 'THE'.
01 str3 PIC X(5) VALUE 'WORLD'.
PROCEDURE  DIVISION.       
    STRING str ' ' str1 ' ' str2 ' ' str3 
    DELIMITED BY SIZE INTO s
STOP RUN.

• C++

std::string s = R"( Earth is a planet.
So is the Jupiter)";

• C#

string s = @"Huey
Dewey
Louie";

• D

auto s = "One,
Two,
Three
";

• D

auto s = r"line1
line2
line3";

• D

auto s = `line1
line2
line3`;

• Dart

var s = """A
multi-line
string""";

• Dart

var s = '''A
multi-line
string''';

• Elixir

s = "Spanning
string
works"

• Elixir

s = ~S"""
This will print multiline
and escape char like \G
"""

• Elixir

s = """
multiline
heredoc
"""

• Erlang

S = "Strings
may span
across multiple lines"
"and they can"
"have as many portions"
"as you want"
"all of them quoted".

• Fortran

  s = "Hello &
      &World"

• Go

s := `Huey
Dewey
Louie`

• Groovy

def s = """line 1
line 2
line 3"""

• Groovy

def s = """\
	line 1
	line 2
	line 3""".stripIndent()

• Haskell

s :: String
s = "We will put a backslash to take a break\
     \and then a backslash to resume"

• Haskell

s = unlines [
     "several"
    ,"lines"
    ,"of"
    ,"text"]

• Java

String s, n = lineSeparator();
s = "line 1" + n;
s = s + "line 2" + n;
s = s + "line 3" + n;
s = s + "line 4";

• Java

String s;
StringBuilder b = new StringBuilder();
Formatter f = new Formatter(b);
f.format("line 1%n");
f.format("line 2%n");
f.format("line 3%n");
f.format("line 4");
f.flush();
s = b.toString();

• Java

String s = "This is a very long string which needs \n" +
           "to wrap across multiple lines because \n" +
           "otherwise my code is unreadable.";

• Java

String s = """
This is a very long string which needs
to wrap across multiple lines because
otherwise my code is unreadable.
""";

• Kotlin

val s =
    """
    This is my
    multi-line string.
    """

• Lisp

(setf s "a
b
c
d")

• Lua

s = [[
Huey
Dewey
Louie
]]

• Lua

s = 'Huey \n'..
'Dewey \n'..
'Louie'

• Lua

local s = "The quick brown fox \z
           jumped over the lazy dog.\
This the second line.  "

• Obj-C

NSString *s=@"Huey\n"
            @"Dewey\n"
            @"Louie";

• Pascal

var 
  s: String;
begin
  s := 'one' + sLineBreak + 'two' + sLineBreak + 'three'
end.

• Pascal

var 
  s: String;
begin
  s := '''
one
two
three
''';
end.

• Pascal

var 
  _s: String;
begin
  _s := 'one' + LineEnding + 'two' + LineEnding + 'three'
end.

• Perl

$s =<<EOSTR;
One of the ways to create multiline text is called
the "here doc" (lifted from various UNIX shells).
A 'here doc' is the <<tag construct.  Perl continues to treat
all the text found as part of the string until there's a line containing
the EOSTR tag at the beginning
EOSTR

• Perl

$s = q{
There are a good few ways to create multiline
text strings in perl.
};

• Perl

$s = "Perl normally allows
strings to contain newlines.";

• Python

s = ('line 1\n'
     'line 2\n'
     'line 3\n'
     'line 4')

• Python

s = """Huey
Dewey
Louie"""

• Ruby

s = "Spanning
string
works"

• Ruby

s = <<EOS
This is a
multi-line string.
We call it a "heredoc"
EOS

• Rust

let s = r#"Huey
Dewey
Louie"#;

• Rust

let s = "line 1
line 2
line 3";

• Scala

val s = """line 1
          |line 2
          |line 3""".stripMargin

• Scala

val s = """line 1
line 2
line 3"""

• Scheme

(define s "This is my multi-line literal.
Line number two!
  This line starts with two spaces.")

• Smalltalk

s := 'Will this compile?
Oh yes, it will!'.

• VB

Dim s as String = "
This
Is
Multiline
Text!"