You can match any single character with a dot (.). A dot means there must be a character in the string.
You can make a single character optional by placing a question mark (?) after it.
Regular Expression
Match
Not a Match
.t
at, xt
ax, xx
m.x
mix
mx, miix
mi?x
mix, mx
miix
m.?x
mix, max, mx
miix, maax