Also, sometimes they make indentation and blank lines clearer. You can include those with multi-line quoted strings, but that's not always as clear. For one thing, you can't justify the first line to the left without adding a newline at the beginning. These are equivalent, and I think the first is clearer:
my $foo = <<END;
paragraph 1
line 2
paragraph 2
line 2
END
my $bar = qq| paragraph 1
line 2
paragraph 2
line 2
|;
|