Comment 1 for bug 1581658

As a work-around, the opac.barcode_regex library setting could be used to identify cases where patron barcodes start with something other than a digit. E.g., if any string that starts with either a digit or with MPL is (likely) a barcode, you could use something like "^(\d|MPL)" as the regex.

This isn't perfect, however -- if there are other patrons not belonging to MPL who nonetheless have usernames starting with "MPL", they would not be able to log in using their username.