Perl has several quoting mechanisms, but the here-doc is the most convenient for quoting multiline strings. You may be familiar with such constructs from shell programming. The basic syntax is to follow doubled left-angle brackets with a terminator string and a semi-colon, all lines after that up to the terminator are quoted.
my $string = <<EOS;
this is part of the string
and so is this
EOS
# now we are out of the quoted string
There are a few points to be aware of: By default, such a string is considered to be double quoted (so variable interpolation works as expected); and the final terminator should be flush with the left margin and by itself on a line (no trailing spaces or tabs or anything else). Thus, even though all the code is indented here, you are to assume that it is flush left. To achieve a single version you surround your initial terminator specifier with single quotes:
my $string = <<'EOS';
this is a
single quoted
here-doc
EOS
Note, all indentation and spacing is preserved, this is simple a multiline string. Besides single or double quotes, you can also use backtics to have your multiline string executed as shell commands:
print <<`SHELL`;
echo Hello
ls -l
SHELL
One good reason to use here-docs is to avoid multiple print statements, say when printing several lines of HTML:
print "<html>\n";
print "<head><title>Whatever</title></head>\n";
print "<body>\n";
# and more of the same
print <<HTML;
<html>
<head><title>Whatever</title></head>
<body>
HTML
Now we’ve avoided explicitly using quotes and newlines and our output is contained in a nice little chunk.
Here-docs can also be stacked, either for direct printing (not so useful perhaps) or when providing multiline quoted strings as arguments to some function:
$two = "this is the second\n";
print <<FIRST, $two, <<THIRD;
Here is the
first string
FIRST
And here is
the third
THIRD
foo(<<FIRST, $two, <<THIRD);
Here is the
first argument
FIRST
And here is
the third
THIRD
sub foo {
my($first, $second, $third) = @_;
print "$first$second$third";
}
The perldata manpage documents here-doc syntax along with a method a allowing for indentation. The faqs (perlfaq4 in particular) also shows several methods of arranging various indentation and block-like formatting of here-docs.