shell: things you never see

x.sh

#
for i
in {0..9}
do
        echo "$i"
done

#
case "$p"
in
        (foo) : ;;
        (*) false
esac

#
: "${\
foo=bar\
}"

# https://github.com/oilshell/oil/issues/3
[[ ('(x=5, y[10]+=5), x*=y[10]' -eq x) && y[2]==y[10]?1:0 -eq 0 ]]

# http://lists.gnu.org/archive/html/help-bash/2017-03/msg00008.html
if(echo -n fo)then(echo o)fi
({(:)})

#
a=([arithmetic, 1+1]= [-1]=foo)

#
echo ${_[up, 1]}

The case-clause in Algol68 was:

 case switch in statements, statements,... [ out statements ] esac
 "brief" form:  ( switch | statements,statements,... | statements )

So, the "out" is missing in sh

for i in x was a new form in the history of for-loops