regex_replace function

I'm trying to replace the following string with offset of 2 characters from beginning and end.

Example input: A9999999999

Expected output: A9********99

I have tried the following but not able to narrow down to exact format

• regexp_replace(a, '[0-9]', '*') as a
• REGEXP_REPLACE(a, '[0-9]', '*', 6) as a
• REGEXP_REPLACE(a, '\1((.*)\4$)', '\1*******\3') as a

REGEXP_REPLACE('A9999999999', '(.{2}).*(.{2})', '\1*******\2')

based on you examples, it looks like your string will always be the same length.

I select the first and last characters in capture groups and use those in the final string