echo ~
echo `~`

cat <<< ~

echo ~/dev
echo ~/does-not-exist # still works

echo ~+ # current dir
echo ~- # old PWD

echo ~dave
echo ~nobody
echo ~john

you can't detect a failure unless you look for string being untouched

foo=~dave
echo "$foo"

foo=~:~dave:~nobody:~john
echo "$foo"

this is useful for PATH

name='dave'
home=~$name

this won't work because of the order of operations

eval echo ~