No UPPERCASE for X509 - Match SubjectDN using regular expression

I’m testing a x509 authentication using a PKI dongle.
I added a mapper attribut from LDAP federation and this attribut is imported with uppercase.
The extract possibility into “X509 - match subjectDN using regular expression” extract the dongle field with lowercase whereas it’s well in uppercase originally.
Is there a solution to transform inside the regex extraction the result and force it to be in uppercase. Or another tips to workaround this ?
Thank you for your feedback.