How to match "any character" in regular expression?

The following should be matched:

AAA123
ABCDEFGH123
XXXX123

can I do: ".*123" ?

Yes, you can. That should work.

• . = any char except newline
• \. = the actual dot character
• .? = .{0,1} = match any char except newline zero or one times
• .* = .{0,} = match any char except newline zero or more times
• .+ = .{1,} = match any char except newline one or more times