Find if cell contents exist in array

I am trying to find a solution so that if the contents of B2 can be found in array DOUBLE!A2:A, it would output B2, else it would output "Cannot be doubled".

I tried =IF(REGEXMATCH(B2, DOUBLE!A2:A), B2, "Cannot be doubled") but it is not working.

Here is an example sheet

Thank you in advance. Hopefully my question is clear enough.

>Solution :

Please try the following:

=IF(ISNUMBER(MATCH(B2, DOUBLE!A2:A, 0)), B2, "Cannot be doubled")