Thanks for the sample! I had a look at the Net::LDAP::LDIF source, and it looks like the encode => 'base64' option only affects the dn:, and attributes are only decided based on what characters they contain, nothing else. So unfortunately, unless you patch* this module, it won't be able to do what you want...

Update: Of course, you could send all of the LDIF files through a "canonicalization" once, so that the diffs later on only show the actual changes. Or, if this is about version control, there are git filters... (not the most elegant solutions, just some ideas)

* Update 2: Here's one way. The disadvantage is of course that if the module author makes changes to Net::LDAP::LDIF::_write_attr, you'd have to carry those over manually.

use warnings;
use strict;
use Data::Dump;
use Net::LDAP::LDIF;

{
    package Net::LDAP::LDIF::B64;
    use parent 'Net::LDAP::LDIF';
    sub _write_attr {
        my($self, $attr, $val) = @_;
        my $lower = $self->{lowercase};
        my $fh = $self->{fh};
        my $b64 = $self->{b64attr};
        my $res = 1;  # result value
        foreach my $v (@$val) {
            my $ln = $lower ? lc $attr : $attr;
            $v = Encode::encode_utf8($v)
            if (Net::LDAP::LDIF::CHECK_UTF8 and Encode::is_utf8($v));
            if ( $v =~ /(^[ :<]|[\x00-\x1f\x7f-\xff]| $)/
                || $b64 && $attr=~$b64 ) {
                require MIME::Base64;
                $ln .= ':: ' . MIME::Base64::encode($v, '');
            }
            else {
                $ln .= ': ' . $v;
            }
            $res &&= print $fh
                Net::LDAP::LDIF::_wrap($ln, $self->{wrap}), "\n";
        }
        $res;
    }
}

our $old_ldif = Net::LDAP::LDIF->new( "dump.ldif", "r",
    onerror => 'undef' );
our $new_ldif = Net::LDAP::LDIF::B64->new( "dump_new.ldif", "w",
    onerror => 'undef', wrap => 76, b64attr => qr/\AuserPassword\z/ );
while (not $old_ldif->eof()) {
    my $entry = $old_ldif->read_entry();
    if ($old_ldif->error()) {
        warn "Error msg: ", $old_ldif->error(), "\n";
        warn "Error lines:\n", $old_ldif->error_lines(), "\n";
    } else {
        # delete attributes no longer needed
        foreach my $attr ($entry->attributes()) {
            if ($attr =~ /^rutgersEduStatus/) {
                $entry->delete($attr);
            }
        }
        $new_ldif->write_entry($entry);
    }
}
$old_ldif->done();
$new_ldif->done();

__END__

--- dump.ldif    2019-07-07 11:03:31.773616611 +0200
+++ dump_new.ldif    2019-07-07 11:43:27.799984355 +0200
@@ -20,6 +20,5 @@
 homePostalAddress: 433 W County Dr$Somerville, NJ 088763470
 postalAddress: R U C S
 rutgersEduDateOfBirth: 1960-01-01
-rutgersEduStatus: active
 uidNumber: 120001
 userPassword:: e1NBU0x9dGVzdGluZ0BSVVRHRVJTLkVEVQ==
[download]

Finally got back to this project and that worked just fine. Don't mind the module patch since this will hopefully be a once and done script.

Thanks so much! -ds