String syntax

Command	Output
echo foo	foo
echo 'foo'	foo
echo "foo"	foo
echo `foo`	`foo`
echo %{foo}	foo
echo %(foo)	foo
echo %sh{foo}
echo %sh{echo foo}	foo
reg a foo;echo %reg{a}	foo
reg a foo;echo %sh{$kak_reg_a}
reg a foo;echo %sh{echo $kak_reg_a}	foo