$ echo {x,y,z}
x y z


$ echo a{x,y,z}
ax ay az 


$ echo {{1,2,3},1,2,3}
1 2 3 1 2 3

$ echo {{1,2,3}1,2,3}
11 21 31 2 3


$ cp /etc/samba/smb.conf{,.bak}

>CTRL + R to search through the history .