Another way. This approach uses highly factored and specific regexes to achieve a high degree of discrimination — if that's what you want! It's easy to add further, highly specialized regexes. ($section is returned as '' (empty atring) if no section is present rather than as undef.) Optional whitespace may exist between page and section sub-fields. Note that with the right pattern anchors, multiple page/section fields can be extracted from a single string/line.

c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(dd);
 ;;
 my $rx_simple = qr{
   [[:alpha:]] [[:alnum:]]* (?: - [[:alnum:]]+)* }xms;
 my $rx_module = qr{
   [[:upper:]] [[:alpha:]]* (?: :: [[:upper:]] [[:alpha:]]*)*
   }xms;
 my $rx_page = qr{ $rx_simple | $rx_module }xms;
 ;;
 my $rx_section = qr{ [(] \d* [)] }xms;
 ;;
 for my $line (qw(
   ftpd(8)  ftpd  dhcp-config(5)  dhcp-config  foo2  foo2(2)  foo-2
   Cache::Cache(3)  Cache::Cache  Foo::Bar::Baz(42)  Foo::Bar::Baz
   ),
   'ftpd (8)',  'dhcp-config   (5)',  'Cache::Cache (3)',
   qw(-foo  foo-  %^&*@!  123  1foo  foo--bar),
   ) {
   my $got_page_section =
   my ($page, $section) =
   $line =~ m{ \A ($rx_page) \s* ($rx_section?) \z }xms;
   ;;
   $page = $section = '???' unless $got_page_section;
   ;;
   print qq{'$line' -> '$page' '$section'};
   }
 ;;
 my $line = 'ftpd(8) -no dhcp-config no- dhcp-config   (5) -- Foo::Bar
+::Baz(42) (999)';
 my @pages;
 push @pages, [ $1, $2 ] while $line =~ m{
   (?<! \S) ($rx_page) \s* ($rx_section?) (?! \S)
   }xmsg;
 dd \@pages;
"
'ftpd(8)' -> 'ftpd' '(8)'
'ftpd' -> 'ftpd' ''
'dhcp-config(5)' -> 'dhcp-config' '(5)'
'dhcp-config' -> 'dhcp-config' ''
'foo2' -> 'foo2' ''
'foo2(2)' -> 'foo2' '(2)'
'foo-2' -> 'foo-2' ''
'Cache::Cache(3)' -> 'Cache::Cache' '(3)'
'Cache::Cache' -> 'Cache::Cache' ''
'Foo::Bar::Baz(42)' -> 'Foo::Bar::Baz' '(42)'
'Foo::Bar::Baz' -> 'Foo::Bar::Baz' ''
'ftpd (8)' -> 'ftpd' '(8)'
'dhcp-config   (5)' -> 'dhcp-config' '(5)'
'Cache::Cache (3)' -> 'Cache::Cache' '(3)'
'-foo' -> '???' '???'
'foo-' -> '???' '???'
'%^&*@!' -> '???' '???'
'123' -> '???' '???'
'1foo' -> '???' '???'
'foo--bar' -> '???' '???'
[
  ["ftpd", "(8)"],
  ["dhcp-config", ""],
  ["dhcp-config", "(5)"],
  ["Foo::Bar::Baz", "(42)"],
]
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