yes, and from perlop,

Quote and Quote-like Operators While we usually think of quotes as literal values, in Perl they function as operators, providing various kinds of interpolating and pattern matching capabilities. Perl provides customary quote characters for these behaviors, but also provides a way for you to choose your quote character for any of them.

nowhere does it imply (to me) that there are situations where you can use " but not qq(), so i would expect to be able to use

print <<qq~DOUBLE~;
$foo
DOUBLE
[download]

but i can't.

and that doesn't explain or demonstrate other weird uses of heredoc syntax, for example,

my @list = (<<HERE, <<THERE, <<EVERYWHERE);
cluck, cluck
HERE
baa, baa
THERE
e i e i o
EVERYWHERE

print "with a ", shift @list, "and a ", shift @list, "singing ", shift
+ @list;
[download]

so i'd still like a tutorial. but maybe i'll have to write it myself.