$ perl -dT 1.dt.pl 

Loading DB routines from perl5db.pl version 1.55
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(1.dt.pl:7):	say "this provides a solid entry point for debugger";
  DB<1> n                                                                       
this provides a solid entry point for debugger
main::(1.dt.pl:9):	print
main::(1.dt.pl:10):	  "Content-Type: text/plain\r\n\r\n",
main::(1.dt.pl:11):	  Data::Dumper->new( [ \%ENV ], ['*ENV'] )->Sortkeys(1)->Useqq(1)->Dump();
  DB<1> s                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:72):
72:	  my($c, $v, $n) = @_;
  DB<1> v                                                                       
69 	# to cause output of arrays and hashes rather than refs.
70 	#
71 	sub new {
72==>	  my($c, $v, $n) = @_;
73 	
74:	  Carp::croak("Usage:  PACKAGE->new(ARRAYREF, [ARRAYREF])")
75 	    unless (defined($v) && (ref($v) eq 'ARRAY'));
76:	  $n = [] unless (defined($n) && (ref($n) eq 'ARRAY'));
77 	
78:	  my($s) = {
  DB<1> p @_                                                                    
Data::DumperARRAY(0x55cf0af7c438)ARRAY(0x55cf0ae9e3e0)
                                                                
...
  DB<8> n                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:78):
78:	  my($s) = {
79:	        level      => 0,           # current recursive depth
80:	        indent     => $Indent,     # various styles of indenting
81:	        trailingcomma => $Trailingcomma, # whether to add comma after last elem
82:	        pad        => $Pad,        # all lines prefixed by this string
83:	        xpad       => "",          # padding-per-level
84:	        apad       => "",          # added padding for hash keys n such
85:	        sep        => "",          # list separator
86:	        pair       => $Pair,    # hash key/value separator: defaults to ' => '
87:	        seen       => {},          # local (nested) refs (id => [name, val])
88:	        todump     => $v,          # values to dump []
89:	        names      => $n,          # optional names for values []
90:	        varname    => $Varname,    # prefix to use for tagging nameless ones
91:	        purity     => $Purity,     # degree to which output is evalable
92:	        useqq      => $Useqq,      # use "" for strings (backslashitis ensues)
93:	        terse      => $Terse,      # avoid name output (where feasible)
94:	        freezer    => $Freezer,    # name of Freezer method for objects
95:	        toaster    => $Toaster,    # name of method to revive objects
96:	        deepcopy   => $Deepcopy,   # do not cross-ref, except to stop recursion
97:	        quotekeys  => $Quotekeys,  # quote hash keys
98:	        'bless'    => $Bless,    # keyword to use for "bless"
  DB<8> n                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:108):
108:	  if ($Indent > 0) {
  DB<8> n                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:109):
109:	    $s->{xpad} = "  ";
  DB<8> n                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:110):
110:	    $s->{sep} = "\n";
  DB<8> n                                                                       
Data::Dumper::new(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:112):
112:	  return bless($s, $c);
  DB<8> p $s                                                                    
HASH(0x55cf0b055668)
  DB<9> p $c                                                                    
Data::Dumper
  DB<10> r                                                                      
scalar context return from Data::Dumper::new: 'apad' => ''
'bless' => 'bless'
'deepcopy' => 0
...
'
'sortkeys' => 0
'terse' => 0
'toaster' => ''
'todump' => ARRAY(0x55cf0af7c438)
   0  HASH(0x55cf0a6457a0)
      'COLORTERM' => 'truecolor'
      'DBUS_SESSION_BUS_ADDRESS' => 'unix:path=/run/user/1000/bus,guid=25f1c2dbc402335e5a6581fd60d50980'
...
      'XDG_SESSION_TYPE' => 'x11'
      'XMODIFIERS' => '@im=ibus'
      '_' => '/usr/bin/perl'
'trailingcomma' => 0
'useperl' => 0
'useqq' => 0
'varname' => 'VAR'
'xpad' => '  '
Data::Dumper::Sortkeys(/usr/lib/x86_64-linux-gnu/perl/5.30/Data/Dumper.pm:716):
716:	  my($s, $v) = @_;
  DB<10> c                                                                      
Content-Type: text/plain

%ENV = (
         "COLORTERM" => "truecolor",
...
         "_" => "/usr/bin/perl"
       );
Debugged program terminated.  Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.
  DB<10> q                                                                      


##</code><code>##

#!/usr/bin/perl -dT

use v5.030;
use warnings;
use Data::Dumper;

say "this provides a solid entry point for debugger";

print
  "Content-Type: text/plain\r\n\r\n",
  Data::Dumper->new( [ \%ENV ], ['*ENV'] )->Sortkeys(1)->Useqq(1)->Dump();