Note: I'm certain that your editor is set up for UTF-8 input from the output you received, but you should convince yourself of that too and then learn how to configure it

I do confirm that:

In Notepad++ Windows,when editor set to utf8 :

use v5.10;
use Data::Dumper;
use Devel::Peek;

print unpack "C*",'Köln';
Dump 'Köln';

75 195 182 108 110
#note that ö has been mapped as two bytes extended ascii values 195 #a
+nd 182

SV = PV(0x27c7b54) at 0x8eef84
  REFCNT = 1
  FLAGS = (PADTMP,POK,READONLY,pPOK)
  PV = 0x8f4724 "K\303\266ln"\0
  CUR = 5
  LEN = 8
[download]

when editor set to iso-8859-1 :

use v5.10;
use Data::Dumper;
use Devel::Peek;

print unpack "C*",'Köln';
Dump 'Köln';

75 246 108 110
#note that ö is represented with a single byte extended #ascii decimal
+ 246

SV = PV(0x2813394) at 0x20cef84
  REFCNT = 1
  FLAGS = (PADTMP,POK,READONLY,pPOK)
  PV = 0x20d4724 "K\366ln"\0
  CUR = 4
  LEN = 8
[download]