heredoc explanation

gistfile1.txt

$ # literal because it's a single-quote string
$ echo '$HOME'
$HOME
$ # interpreted because it's a double-quote string
$ echo "$HOME"
/home/paradigm
$ # interpreted again because it's a double-quote string despite containing single quotes within it
$ echo "'$HOME'"
'/home/paradigm'
$ # to print the literal with the interpreted string, have to escape
$ echo "\$HOME"
$HOME
$ # interpreted because it's a heredoc
$ cat <<EOF
heredoc> $HOME
heredoc> EOF
/home/paradigm
$ # interpreted again because it's a here-doc despite containing single quotes within it
$ cat <<EOF
heredoc> '$HOME'
heredoc> EOF
'/home/paradigm'
$ # to print the literal with the interpreted string, have to escape
$ cat <<EOF
heredoc> \$HOME
heredoc> EOF
$HOME