$self->_check_for_duplicate_username() is fails after ten duplicates

my @suffixes = ( '', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'10','11','12','13','14','15','16','17','18','19' );

This routine guarantees unique user names for the first 10, now 20, users who create an account with the exact same first initial and last name. After that it returns 0. I expanded the array of suffixes and added a WARN'ing to the logs. But this subroutine will need a new algorythm soon after deployment.