I get the following when installing/removing packages:

Use of uninitialized value in substitution (s///) at
/usr/share/ perl5/Debconf/ Format/ 822.pm line 57, <$__ANONIO__> line 1.
Use of uninitialized value in substitution (s///) at
/usr/share/ perl5/Debconf/ Format/ 822.pm line 57, <$__ANONIO__> line 4.
Use of uninitialized value in substitution (s///) at
/usr/share/ perl5/Debconf/ Format/ 822.pm line 57, <$__ANONIO__> line 5.
Use of uninitialized value in substitution (s///) at
/usr/share/ perl5/Debconf/ Format/ 822.pm line 57, <$__ANONIO__> line 6.
Use of uninitialized value in hash element at
/usr/share/ perl5/Debconf/ DbDriver/ File.pm line 51, <$__ANONIO__> chunk 15.

I'm no expert but it seems to be related to the following bit of code in 822.pm:

my $invars=0;
my $line;
while ($line = <$fh>) {
        chomp $line;
        last if $line eq ''; # blank line is our record delimiter
        if ($invars) {
                if ($line =~ /^\s/) {
                           $line =~ s/^\s+//;
                           my ($var, $value) =split( /\s*=\s? /, $line, 2);
                           $value= ~s/\\n/ \n/g;
                           $ret{ variables} ->{$var} =$value;
                           next;
                }
                  else {
                           $invars= 0;
                }
        }
        ... blah, blah, blah ...
}

IIRC $invars=0 will cause it to evaluate to boolean false, in which case it will
get set to 0 again which makes no sense. Because $invars is set to 0 this means
that the first code block of the if statement gets skipped and $value doesn't
get set which leads to an error when we get to:

elsif (length $key) {
         $value= ~s/\\n/ \n/g;
         $ret{fields} ->{$key} =$value;
}

So it looks to my untrained eye as if $invars should initially be set to 1.