Implementation
Perl

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Be useful.

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Other implementations
s = """Huey
Dewey
Louie"""
s := `Huey
Dewey
Louie`
let s = "line 1
line 2
line 3";
$s = "This string 
is spanning
three lines";
auto str = "One,
Two,
Three
";
var s = '''A
multi-line
string''';
var 
  _s: String;
begin
  _s := 'one' + LineEnding + 'two' + LineEnding + 'three'
end.
s = "Spanning
string
works"
s = "Spanning
string
works"
s = "several\n" ++
    "lines\nof\ntext\n"
S = "Strings
may span
across multiple lines"
"and they can"
"have as many portions"
"as you want"
"all of them quoted".
s = [[
Huey
Dewey
Louie
]]
auto s = ` line1
line2
line3`;

auto r = r" line1
line2
line3`;
string s = @"Huey
Dewey
Louie";
s = """
multiline
heredoc
"""
char *s = "Huey\n"
          "Dewey\n"
          "Louie";
let s = "This is a very long string which needs " +
        "to wrap across multiple lines because " +
        "otherwise my code is unreadable.";
let s = "This is a very long string which needs \
to wrap across multiple lines because \
otherwise my code is unreadable.";
let s = `This is a very long string which needs 
to wrap across multiple lines because 
otherwise my code is unreadable.`;