Use just 'return' instead of 'return undef' in perl code

This makes sure the functions always return the appropriate value
independent of the context.

Fixes Subroutines::ProhibitExplicitReturnUndef.

Warned-by: perlcritic

26 files changed, 94 insertions, 97 deletions

diff --git a/dselect/methods/Debian/Dselect/Ftp.pm b/dselect/methods/Debian/Dselect/Ftp.pm
index 37fe896f7..f750b42ab 100644
--- a/dselect/methods/Debian/Dselect/Ftp.pm
+++ b/dselect/methods/Debian/Dselect/Ftp.pm
@@ -311,7 +311,7 @@ sub do_mdtm {
 	    ) {
 	    $has_mdtm = 0;
 	} elsif (!$ftp->ok()) {
-	    return undef;
+	    return;
 	}
     #}
 
@@ -320,7 +320,7 @@ sub do_mdtm {
 
 	my @files = $ftp->dir($file);
 	if (($#files == -1) || ($ftp->code == 550)) { # No such file or directory
-	    return undef;
+	    return;
 	}
 
 #	my $code=$ftp->code();	my $message=$ftp->message();
diff --git a/scripts/Dpkg/Arch.pm b/scripts/Dpkg/Arch.pm
index bfc19f4e9..3ee450afc 100644
--- a/scripts/Dpkg/Arch.pm
+++ b/scripts/Dpkg/Arch.pm
@@ -253,7 +253,7 @@ sub debtriplet_to_gnutriplet(@)
 
     my ($abi, $os, $cpu) = @_;
 
-    return undef unless defined($abi) && defined($os) && defined($cpu) &&
+    return unless defined($abi) && defined($os) && defined($cpu) &&
         exists($cputable{$cpu}) && exists($ostable{"$abi-$os"});
     return join("-", $cputable{$cpu}, $ostable{"$abi-$os"});
 }
@@ -261,9 +261,9 @@ sub debtriplet_to_gnutriplet(@)
 sub gnutriplet_to_debtriplet($)
 {
     my ($gnu) = @_;
-    return undef unless defined($gnu);
+    return unless defined($gnu);
     my ($gnu_cpu, $gnu_os) = split(/-/, $gnu, 2);
-    return undef unless defined($gnu_cpu) && defined($gnu_os);
+    return unless defined($gnu_cpu) && defined($gnu_os);
 
     read_cputable();
     read_ostable();
@@ -284,7 +284,7 @@ sub gnutriplet_to_debtriplet($)
 	}
     }
 
-    return undef if !defined($cpu) || !defined($os);
+    return if !defined($cpu) || !defined($os);
     return (split(/-/, $os, 2), $cpu);
 }
 
@@ -314,11 +314,11 @@ sub debtriplet_to_debarch(@)
     my ($abi, $os, $cpu) = @_;
 
     if (!defined($abi) || !defined($os) || !defined($cpu)) {
-	return undef;
+	return;
     } elsif (exists $debtriplet_to_debarch{"$abi-$os-$cpu"}) {
 	return $debtriplet_to_debarch{"$abi-$os-$cpu"};
     } else {
-	return undef;
+	return;
     }
 }
 
@@ -341,7 +341,7 @@ sub debarch_to_debtriplet($)
     if (defined($triplet)) {
 	return split('-', $triplet, 3);
     } else {
-	return undef;
+	return;
     }
 }
 
@@ -386,7 +386,7 @@ sub debarch_to_cpuattrs($)
 
         return ($abibits{$abi} || $cpubits{$cpu}, $cpuendian{$cpu});
     } else {
-        return undef;
+        return;
     }
 }
 
diff --git a/scripts/Dpkg/Changelog.pm b/scripts/Dpkg/Changelog.pm
index 42f877d42..0ceda5c5c 100644
--- a/scripts/Dpkg/Changelog.pm
+++ b/scripts/Dpkg/Changelog.pm
@@ -332,15 +332,14 @@ sub get_range {
 	return @$res if wantarray;
 	return $res;
     } else {
-	return () if wantarray;
-	return undef;
+	return;
     }
 }
 
 sub _data_range {
     my ($self, $range) = @_;
 
-    my $data = $self->{data} or return undef;
+    my $data = $self->{data} or return;
 
     return [ @$data ] if $range->{all};
 
@@ -389,7 +388,7 @@ sub _data_range {
     }
 
     return \@result if scalar(@result);
-    return undef;
+    return;
 }
 
 =item $c->abort_early()
@@ -518,7 +517,7 @@ BEGIN {
 sub dpkg {
     my ($self, $range) = @_;
 
-    my @data = $self->get_range($range) or return undef;
+    my @data = $self->get_range($range) or return;
     my $entry = shift @data;
 
     my $f = Dpkg::Control::Changelog->new();
@@ -583,7 +582,7 @@ the remarks about which values are taken from the first entry).
 sub rfc822 {
     my ($self, $range) = @_;
 
-    my @data = $self->get_range($range) or return undef;
+    my @data = $self->get_range($range) or return;
     my $index = Dpkg::Index->new(type => CTRL_CHANGELOG);
 
     foreach my $entry (@data) {
diff --git a/scripts/Dpkg/Changelog/Entry.pm b/scripts/Dpkg/Changelog/Entry.pm
index eb79b8f8f..e434103d5 100644
--- a/scripts/Dpkg/Changelog/Entry.pm
+++ b/scripts/Dpkg/Changelog/Entry.pm
@@ -214,7 +214,7 @@ Return the name of the source package associated to the changelog entry.
 =cut
 
 sub get_source {
-    return undef;
+    return;
 }
 
 =item my $ver = $entry->get_version()
@@ -224,7 +224,7 @@ Return the version associated to the changelog entry.
 =cut
 
 sub get_version {
-    return undef;
+    return;
 }
 
 =item my @dists = $entry->get_distributions()
@@ -234,8 +234,7 @@ Return a list of target distributions for this version.
 =cut
 
 sub get_distributions {
-    return () if wantarray;
-    return undef;
+    return;
 }
 
 =item $fields = $entry->get_optional_fields()
@@ -256,7 +255,7 @@ Return the urgency of the associated upload.
 =cut
 
 sub get_urgency {
-    return undef;
+    return;
 }
 
 =item my $maint = $entry->get_maintainer()
@@ -266,7 +265,7 @@ Return the string identifying the person who signed this changelog entry.
 =cut
 
 sub get_maintainer {
-    return undef;
+    return;
 }
 
 =item my $time = $entry->get_timestamp()
@@ -276,7 +275,7 @@ Return the timestamp of the changelog entry.
 =cut
 
 sub get_timestamp {
-    return undef;
+    return;
 }
 
 =item my $str = $entry->get_dpkg_changes()
diff --git a/scripts/Dpkg/Changelog/Entry/Debian.pm b/scripts/Dpkg/Changelog/Entry/Debian.pm
index 64554806d..48e21ce9d 100644
--- a/scripts/Dpkg/Changelog/Entry/Debian.pm
+++ b/scripts/Dpkg/Changelog/Entry/Debian.pm
@@ -183,7 +183,7 @@ sub get_source {
     if (defined($self->{header}) and $self->{header} =~ $regex_header) {
 	return $1;
     }
-    return undef;
+    return;
 }
 
 sub get_version {
@@ -191,7 +191,7 @@ sub get_version {
     if (defined($self->{header}) and $self->{header} =~ $regex_header) {
 	return Dpkg::Version->new($2);
     }
-    return undef;
+    return;
 }
 
 sub get_distributions {
@@ -203,8 +203,7 @@ sub get_distributions {
 	return @dists if wantarray;
 	return $dists[0];
     }
-    return () if wantarray;
-    return undef;
+    return;
 }
 
 sub get_optional_fields {
@@ -233,7 +232,7 @@ sub get_urgency {
 	$f->{Urgency} =~ s/\s.*$//;
 	return lc($f->{Urgency});
     }
-    return undef;
+    return;
 }
 
 sub get_maintainer {
@@ -241,7 +240,7 @@ sub get_maintainer {
     if (defined($self->{trailer}) and $self->{trailer} =~ $regex_trailer) {
 	return "$1 <$2>";
     }
-    return undef;
+    return;
 }
 
 sub get_timestamp {
@@ -249,7 +248,7 @@ sub get_timestamp {
     if (defined($self->{trailer}) and $self->{trailer} =~ $regex_trailer) {
 	return $4;
     }
-    return undef;
+    return;
 }
 
 =back
diff --git a/scripts/Dpkg/Changelog/Parse.pm b/scripts/Dpkg/Changelog/Parse.pm
index 399033fe9..f6d7e2d53 100644
--- a/scripts/Dpkg/Changelog/Parse.pm
+++ b/scripts/Dpkg/Changelog/Parse.pm
@@ -156,7 +156,7 @@ sub changelog_parse {
 	return @res;
     } else {
 	return $res[0] if (@res);
-	return undef;
+	return;
     }
 }
 
diff --git a/scripts/Dpkg/Checksums.pm b/scripts/Dpkg/Checksums.pm
index fd4ba0ccc..1d4e14140 100644
--- a/scripts/Dpkg/Checksums.pm
+++ b/scripts/Dpkg/Checksums.pm
@@ -99,7 +99,7 @@ by the program that generates it).
 
 sub checksums_get_property($$) {
     my ($alg, $property) = @_;
-    return undef unless checksums_is_supported($alg);
+    return unless checksums_is_supported($alg);
     return $CHECKSUMS->{lc($alg)}{$property};
 }
 
@@ -315,7 +315,7 @@ sub get_checksum {
 	return $self->{checksums}{$file} unless defined $alg;
 	return $self->{checksums}{$file}{$alg};
     }
-    return undef;
+    return;
 }
 
 =item $size = $ck->get_size($file)
diff --git a/scripts/Dpkg/Compression.pm b/scripts/Dpkg/Compression.pm
index c83fb4e25..322cb5ff3 100644
--- a/scripts/Dpkg/Compression.pm
+++ b/scripts/Dpkg/Compression.pm
@@ -129,9 +129,9 @@ the name of the decompression program.
 
 sub compression_get_property {
     my ($comp, $property) = @_;
-    return undef unless compression_is_supported($comp);
+    return unless compression_is_supported($comp);
     return $COMP->{$comp}{$property} if exists $COMP->{$comp}{$property};
-    return undef;
+    return;
 }
 
 =item compression_guess_from_filename($filename)
@@ -149,7 +149,7 @@ sub compression_guess_from_filename {
 	    return $comp;
         }
     }
-    return undef;
+    return;
 }
 
 =item my $comp = compression_get_default()
diff --git a/scripts/Dpkg/Compression/FileHandle.pm b/scripts/Dpkg/Compression/FileHandle.pm
index b0aff7b35..e7c9082c1 100644
--- a/scripts/Dpkg/Compression/FileHandle.pm
+++ b/scripts/Dpkg/Compression/FileHandle.pm
@@ -228,7 +228,7 @@ sub CLOSE {
 sub FILENO {
     my ($self) = shift;
     return *$self->{"file"}->fileno(@_) if defined *$self->{"file"};
-    return undef;
+    return;
 }
 
 sub EOF {
@@ -252,7 +252,7 @@ sub TELL {
 sub BINMODE {
     my ($self) = shift;
     return *$self->{"file"}->binmode(@_) if defined *$self->{"file"};
-    return undef;
+    return;
 }
 
 ##
diff --git a/scripts/Dpkg/Control/Fields.pm b/scripts/Dpkg/Control/Fields.pm
index a703c45c1..56ae2f126 100644
--- a/scripts/Dpkg/Control/Fields.pm
+++ b/scripts/Dpkg/Control/Fields.pm
@@ -408,7 +408,7 @@ Undef is returned for non-official fields.
 sub field_is_allowed_in($@) {
     my ($field, @types) = @_;
     $field = field_capitalize($field);
-    return undef unless field_is_official($field);
+    return unless field_is_official($field);
 
     return 0 if not scalar(@types);
     foreach my $type (@types) {
@@ -468,7 +468,7 @@ sub field_transfer_single($$;$) {
         warning(_g("unknown information field '%s' in input data in %s"),
                 $field, $from->get_option("name") || _g("control information"));
     }
-    return undef;
+    return;
 }
 
 =item field_transfer_all($from, $to)
@@ -549,9 +549,9 @@ Breaks, ...). Returns undef for fields which are not dependencies.
 
 sub field_get_dep_type($) {
     my $field = field_capitalize($_[0]);
-    return undef unless field_is_official($field);
+    return unless field_is_official($field);
     return $FIELDS{$field}{'dependency'} if exists $FIELDS{$field}{'dependency'};
-    return undef;
+    return;
 }
 
 =item field_register($field, $allowed_types, %opts)
diff --git a/scripts/Dpkg/Control/Hash.pm b/scripts/Dpkg/Control/Hash.pm
index b14287642..38ed1edc7 100644
--- a/scripts/Dpkg/Control/Hash.pm
+++ b/scripts/Dpkg/Control/Hash.pm
@@ -258,7 +258,7 @@ sub find_custom_field {
     foreach my $key (keys %$self) {
         return $key if $key =~ /^X[SBC]*-\Q$name\E$/i;
     }
-    return undef;
+    return;
 }
 
 =item $c->get_custom_field($name)
@@ -271,7 +271,7 @@ sub get_custom_field {
     my ($self, $name) = @_;
     my $key = $self->find_custom_field($name);
     return $self->{$key} if defined $key;
-    return undef;
+    return;
 }
 
 =item $c->save($filename)
@@ -442,7 +442,7 @@ sub FETCH {
     my ($self, $key) = @_;
     $key = lc($key);
     return $self->[0]->{$key} if exists $self->[0]->{$key};
-    return undef;
+    return;
 }
 
 sub STORE {
@@ -494,7 +494,7 @@ sub NEXTKEY {
 	    $found = 1 if $_ eq $last;
 	}
     }
-    return undef;
+    return;
 }
 
 1;
diff --git a/scripts/Dpkg/Control/Info.pm b/scripts/Dpkg/Control/Info.pm
index b4009e8e2..e88bcb8f0 100644
--- a/scripts/Dpkg/Control/Info.pm
+++ b/scripts/Dpkg/Control/Info.pm
@@ -154,7 +154,7 @@ sub get_pkg_by_name {
     foreach my $pkg (@{$self->{packages}}) {
 	return $pkg if ($pkg->{Package} eq $name);
     }
-    return undef;
+    return;
 }
 
 
diff --git a/scripts/Dpkg/Deps.pm b/scripts/Dpkg/Deps.pm
index c4ad92a0f..d641b7d7f 100644
--- a/scripts/Dpkg/Deps.pm
+++ b/scripts/Dpkg/Deps.pm
@@ -167,8 +167,8 @@ sub deps_eval_implication {
     my ($rel_p, $v_p, $rel_q, $v_q) = @_;
 
     # If versions are not valid, we can't decide of any implication
-    return undef unless defined($v_p) and $v_p->is_valid();
-    return undef unless defined($v_q) and $v_q->is_valid();
+    return unless defined($v_p) and $v_p->is_valid();
+    return unless defined($v_q) and $v_q->is_valid();
 
     # q wants an exact version, so p must provide that exact version.  p
     # disproves q if q's version is outside the range enforced by p.
@@ -239,7 +239,7 @@ sub deps_eval_implication {
         }
     }
 
-    return undef;
+    return;
 }
 
 =item my $dep = deps_concat(@dep_list)
@@ -317,7 +317,7 @@ sub deps_parse {
 	                                             $options{build_dep});
 	    if (not defined $dep_simple->{package}) {
 		warning(_g("can't parse dependency %s"), $dep_or);
-		return undef;
+		return;
 	    }
 	    $dep_simple->{arches} = undef if not $options{use_arch};
             if ($options{reduce_arch}) {
@@ -344,7 +344,7 @@ sub deps_parse {
     foreach my $dep (@dep_list) {
         if ($options{union} and not $dep->isa("Dpkg::Deps::Simple")) {
             warning(_g("an union dependency can only contain simple dependencies"));
-            return undef;
+            return;
         }
         $dep_and->add($dep);
     }
@@ -643,14 +643,14 @@ sub implies {
     my ($self, $o) = @_;
     if ($o->isa('Dpkg::Deps::Simple')) {
 	# An implication is only possible on the same package
-	return undef if $self->{package} ne $o->{package};
+	return if $self->{package} ne $o->{package};
 
 	# Our architecture set must be a superset of the architectures for
 	# o, otherwise we can't conclude anything.
-	return undef unless Dpkg::Deps::_arch_is_superset($self->{arches}, $o->{arches});
+	return unless Dpkg::Deps::_arch_is_superset($self->{arches}, $o->{arches});
 
 	# The arch qualifier must not forbid an implication
-	return undef unless
+	return unless
 	    Dpkg::Deps::_arch_qualifier_allows_implication($self->{archqual},
 	                                                   $o->{archqual});
 
@@ -658,7 +658,7 @@ sub implies {
 	return 1 if not defined $o->{relation};
 	# If o has a version clause, we must also have one, otherwise there
 	# can't be an implication
-	return undef if not defined $self->{relation};
+	return if not defined $self->{relation};
 
 	return Dpkg::Deps::deps_eval_implication($self->{relation},
 		$self->{version}, $o->{relation}, $o->{version});
@@ -761,7 +761,7 @@ sub has_arch_restriction {
 
 sub get_evaluation {
     my ($self, $facts) = @_;
-    return undef if not defined $self->{package};
+    return if not defined $self->{package};
     return $facts->_evaluate_simple_dep($self);
 }
 
@@ -956,7 +956,7 @@ sub implies {
 	}
 	return 1 if $subset;
     }
-    return undef;
+    return;
 }
 
 sub get_evaluation {
@@ -1064,7 +1064,7 @@ sub implies {
 	}
 	return 1 if $subset;
     }
-    return undef;
+    return;
 }
 
 sub get_evaluation {
@@ -1150,12 +1150,12 @@ sub output {
 
 sub implies {
     # Implication test are not useful on Union
-    return undef;
+    return;
 }
 
 sub get_evaluation {
     # Evaluation are not useful on Union
-    return undef;
+    return;
 }
 
 sub simplify_deps {
@@ -1272,7 +1272,7 @@ sub check_package {
 sub _find_package {
     my ($self, $dep, $lackinfos) = @_;
     my ($pkg, $archqual) = ($dep->{package}, $dep->{archqual});
-    return undef if not exists $self->{pkg}{$pkg};
+    return if not exists $self->{pkg}{$pkg};
     my $host_arch = $dep->{host_arch};
     my $build_arch = $dep->{build_arch};
     foreach my $p (@{$self->{pkg}{$pkg}}) {
@@ -1293,7 +1293,7 @@ sub _find_package {
 	    return $p if $a eq $archqual;
 	}
     }
-    return undef;
+    return;
 }
 
 sub _find_virtual_packages {
@@ -1324,7 +1324,7 @@ sub _evaluate_simple_dep {
 	next if defined $dep->{relation}; # Provides don't satisfy versioned deps
 	return 1;
     }
-    return undef if $lackinfos;
+    return if $lackinfos;
     return 0;
 }
 
diff --git a/scripts/Dpkg/Index.pm b/scripts/Dpkg/Index.pm
index 12ca1e9ab..7dd650fd9 100644
--- a/scripts/Dpkg/Index.pm
+++ b/scripts/Dpkg/Index.pm
@@ -202,7 +202,7 @@ Returns the item identified by $key or undef.
 sub get_by_key {
     my ($self, $key) = @_;
     return $self->{'items'}{$key} if exists $self->{'items'}{$key};
-    return undef;
+    return;
 }
 
 =item my @keys = $index->get_keys(%criteria)
diff --git a/scripts/Dpkg/Package.pm b/scripts/Dpkg/Package.pm
index b68040822..f3ed4698c 100644
--- a/scripts/Dpkg/Package.pm
+++ b/scripts/Dpkg/Package.pm
@@ -36,7 +36,7 @@ sub pkg_name_is_illegal($) {
     $name =~ m/^[0-9a-z]/o ||
         return _g("must start with an alphanumeric character");
 
-    return undef;
+    return;
 }
 
 1;
diff --git a/scripts/Dpkg/Path.pm b/scripts/Dpkg/Path.pm
index 383bc0d00..5a8977037 100644
--- a/scripts/Dpkg/Path.pm
+++ b/scripts/Dpkg/Path.pm
@@ -66,7 +66,7 @@ sub get_pkg_root_dir($) {
 	last if $file !~ m{/};
 	$file =~ s{/+[^/]+$}{};
     }
-    return undef;
+    return;
 }
 
 =item relative_to_pkg_root($file)
@@ -82,7 +82,7 @@ sub relative_to_pkg_root($) {
 	$pkg_root .= "/";
 	return $file if ($file =~ s/^\Q$pkg_root\E//);
     }
-    return undef;
+    return;
 }
 
 =item guess_pkg_root_dir($file)
@@ -112,7 +112,7 @@ sub guess_pkg_root_dir($) {
 	$file = $parent;
 	last if $file !~ m{/};
     }
-    return undef;
+    return;
 }
 
 =item check_files_are_the_same($file1, $file2, $resolve_symlink)
@@ -185,7 +185,7 @@ canonicalized by canonpath().
 sub resolve_symlink($) {
     my $symlink = shift;
     my $content = readlink($symlink);
-    return undef unless defined $content;
+    return unless defined $content;
     if (File::Spec->file_name_is_absolute($content)) {
 	return canonpath($content);
     } else {
@@ -214,7 +214,7 @@ sub find_command($) {
 	    return "$dir/$cmd" if -x "$dir/$cmd";
 	}
     }
-    return undef;
+    return;
 }
 
 =item my $control_file = get_control_path($pkg, $filetype)
@@ -236,7 +236,7 @@ sub get_control_path($;$) {
     spawn(exec => \@exec, wait_child => 1, to_string => \$control_file);
     chomp($control_file);
     if (defined $filetype) {
-	return undef if $control_file eq "";
+	return if $control_file eq "";
 	return $control_file;
     }
     return () if $control_file eq "";
@@ -267,7 +267,7 @@ sub find_build_file($) {
     }
     return @files if wantarray;
     return $files[0] if scalar @files;
-    return undef;
+    return;
 }
 
 =back
diff --git a/scripts/Dpkg/Shlibs.pm b/scripts/Dpkg/Shlibs.pm
index 722504d5a..1a40b8f1a 100644
--- a/scripts/Dpkg/Shlibs.pm
+++ b/scripts/Dpkg/Shlibs.pm
@@ -127,7 +127,7 @@ sub find_library {
 	    }
 	}
     }
-    return undef;
+    return;
 }
 
 1;
diff --git a/scripts/Dpkg/Shlibs/Objdump.pm b/scripts/Dpkg/Shlibs/Objdump.pm
index e03b5e81c..5652035cb 100644
--- a/scripts/Dpkg/Shlibs/Objdump.pm
+++ b/scripts/Dpkg/Shlibs/Objdump.pm
@@ -66,7 +66,7 @@ sub locate_symbol {
 	    return $sym;
 	}
     }
-    return undef;
+    return;
 }
 
 sub get_object {
@@ -74,7 +74,7 @@ sub get_object {
     if ($self->has_object($objid)) {
 	return $self->{objects}{$objid};
     }
-    return undef;
+    return;
 }
 
 sub has_object {
@@ -379,7 +379,7 @@ sub get_symbol {
             return $self->{dynsyms}{$name . '@Base'};
         }
     }
-    return undef;
+    return;
 }
 
 sub get_exported_dynamic_symbols {
diff --git a/scripts/Dpkg/Shlibs/Symbol.pm b/scripts/Dpkg/Shlibs/Symbol.pm
index 193ee1e5d..b1d649eca 100644
--- a/scripts/Dpkg/Shlibs/Symbol.pm
+++ b/scripts/Dpkg/Shlibs/Symbol.pm
@@ -81,7 +81,7 @@ sub parse_tagspec {
 	}
 	return $rest;
     }
-    return undef;
+    return;
 }
 
 sub parse_symbolspec {
@@ -346,7 +346,7 @@ sub get_pattern_matches {
 # and add it to the pattern matches list.
 sub create_pattern_match {
     my $self = shift;
-    return undef unless $self->is_pattern();
+    return unless $self->is_pattern();
 
     # Leave out 'pattern' subfield while deep-cloning
     my $pattern_stuff = $self->{pattern};
@@ -381,7 +381,7 @@ sub convert_to_alias {
 	    return cppfilt_demangle_cpp($rawname);
 	}
     }
-    return undef;
+    return;
 }
 
 sub get_tagspec {
diff --git a/scripts/Dpkg/Shlibs/SymbolFile.pm b/scripts/Dpkg/Shlibs/SymbolFile.pm
index cb24fc5f3..7b6eb2b50 100644
--- a/scripts/Dpkg/Shlibs/SymbolFile.pm
+++ b/scripts/Dpkg/Shlibs/SymbolFile.pm
@@ -160,7 +160,7 @@ sub create_symbol {
 	$symbol->initialize(arch => $self->get_arch());
 	return $symbol;
     }
-    return undef;
+    return;
 }
 
 sub add_symbol {
@@ -376,7 +376,7 @@ sub find_matching_pattern {
 		( symbol => $pattern, soname => $soname ) : $pattern;
 	}
     }
-    return (wantarray) ? () : undef;
+    return;
 }
 
 # merge_symbols($object, $minver)
@@ -505,7 +505,7 @@ sub get_field {
 	    return $obj->{fields}{$name};
 	}
     }
-    return undef;
+    return;
 }
 
 # Tries to find a symbol like the $refsym and returns its descriptor.
@@ -525,7 +525,7 @@ sub lookup_symbol {
 	    }
 	}
     }
-    return (wantarray) ? () : undef;
+    return;
 }
 
 # Tries to find a pattern like the $refpat and returns its descriptor.
@@ -561,7 +561,7 @@ sub lookup_pattern {
 	    }
 	}
     }
-    return (wantarray) ? () : undef;
+    return;
 }
 
 # Get symbol object reference either by symbol name or by a reference object.
diff --git a/scripts/Dpkg/Source/Quilt.pm b/scripts/Dpkg/Source/Quilt.pm
index 543a760cd..e61331f91 100644
--- a/scripts/Dpkg/Source/Quilt.pm
+++ b/scripts/Dpkg/Source/Quilt.pm
@@ -118,7 +118,7 @@ sub top {
     my ($self) = @_;
     my $count = scalar @{$self->{'applied-patches'}};
     return $self->{'applied-patches'}[$count - 1] if $count;
-    return undef;
+    return;
 }
 
 sub next {
@@ -126,7 +126,7 @@ sub next {
     my $count_applied = scalar @{$self->{'applied-patches'}};
     my $count_series = scalar @{$self->{'series'}};
     return $self->{'series'}[$count_applied] if ($count_series > $count_applied);
-    return undef;
+    return;
 }
 
 sub push {
@@ -202,7 +202,7 @@ sub get_db_version {
         close(VER);
         return $version;
     }
-    return undef;
+    return;
 }
 
 sub find_problems {
@@ -215,7 +215,7 @@ sub find_problems {
     if (-e $series and not -f _) {
         return sprintf(_g("%s should be a file or non-existing"), $series);
     }
-    return undef;
+    return;
 }
 
 sub get_series_file {
diff --git a/scripts/Dpkg/Vendor.pm b/scripts/Dpkg/Vendor.pm
index e61818e31..e3ec1679c 100644
--- a/scripts/Dpkg/Vendor.pm
+++ b/scripts/Dpkg/Vendor.pm
@@ -72,7 +72,7 @@ if there's no file for the given vendor.
 sub get_vendor_info(;$) {
     my $vendor = shift || "default";
     my $file = get_vendor_file($vendor);
-    return undef unless $file;
+    return unless $file;
     my $fields = Dpkg::Control::Hash->new();
     $fields->load($file) || error(_g("%s is empty"), $file);
     return $fields;
@@ -114,7 +114,7 @@ sub get_current_vendor() {
     }
     $f = get_vendor_info();
     return $f->{'Vendor'} if defined $f;
-    return undef;
+    return;
 }
 
 =item $object = Dpkg::Vendor::get_vendor_object($name)
diff --git a/scripts/Dpkg/Vendor/Default.pm b/scripts/Dpkg/Vendor/Default.pm
index ee2d495b4..4bc44c211 100644
--- a/scripts/Dpkg/Vendor/Default.pm
+++ b/scripts/Dpkg/Vendor/Default.pm
@@ -126,8 +126,7 @@ sub run_hook {
     }
 
     # Default return value for unknown/unimplemented hooks
-    return () if wantarray;
-    return undef;
+    return;
 }
 
 =back
diff --git a/scripts/Dpkg/Version.pm b/scripts/Dpkg/Version.pm
index a113c5815..d4944c80e 100644
--- a/scripts/Dpkg/Version.pm
+++ b/scripts/Dpkg/Version.pm
@@ -84,7 +84,7 @@ sub new {
     $ver = "$ver" if ref($ver); # Try to stringify objects
 
     if ($opts{'check'}) {
-	return undef unless version_check($ver);
+	return unless version_check($ver);
     }
 
     my $self = {};
diff --git a/scripts/dpkg-shlibdeps.pl b/scripts/dpkg-shlibdeps.pl
index f4cc571c2..fc570bc3c 100755
--- a/scripts/dpkg-shlibdeps.pl
+++ b/scripts/dpkg-shlibdeps.pl
@@ -587,7 +587,7 @@ sub get_min_version_from_deps {
 	{
 	    return $dep->{version};
 	}
-	return undef;
+	return;
     } else {
 	my $res;
 	foreach my $subdep ($dep->get_deps()) {
@@ -737,7 +737,7 @@ sub find_symbols_file {
 	    return $file;
 	}
     }
-    return undef;
+    return;
 }
 
 sub symfile_has_soname {
@@ -814,7 +814,7 @@ sub my_find_library {
     $file = find_library($lib, \@RPATH, $format, "");
     return $file if defined($file);
 
-    return undef;
+    return;
 }
 
 my %cached_pkgmatch = ();
diff --git a/test/100_critic.t b/test/100_critic.t
index eac78ca60..8c768276f 100644
--- a/test/100_critic.t
+++ b/test/100_critic.t
@@ -58,6 +58,7 @@ my @policies = qw(
     Modules::RequireEndWithOne
     Modules::RequireExplicitPackage
     Modules::RequireFilenameMatchesPackage
+    Subroutines::ProhibitExplicitReturnUndef
     TestingAndDebugging::ProhibitNoStrict
     TestingAndDebugging::ProhibitNoWarnings
     ValuesAndExpressions::ProhibitComplexVersion