When faced by these sort of problems it is a good practice to dump out the data structure you think you are dealing with, I use YAML, others swear by Data::Dumper. Which ever you choose it will help.

One problem is that $xml doesn't have a key called tc, it has a key called dut, dumping out $xml would have shown that. The other is that you want to use result as a key but XML::Simple will use the value of the first attribute as a key. This is some code that works on the example provided. I don't know if it will work on the full set of data.

use XML::Simple;

my $XML_string=<<'XML';
<exec>
   <dut>
      <tc id="001.001" result="Passed">
         <ts/>
      </tc>
      <tc id="002.001" result="Failed">
         <ts/>
      </tc>
      <tc id="003.001" result="Warnings">
         <ts/>
      </tc>
   </dut>
</exec>
XML

# create object
my $xmlfile = XML::Simple->new(KeyAttr =>  {result => 'result'} );
my $xml = $xmlfile->XMLin($XML_string);

my $Passed = 0;
my $Warnings = 0;
my $Failed = 0;

print Dump $XML;
foreach my $TCresult (@{$xml->{dut}{tc}}){
    print Dump $TCresult;
   if ($TCresult->{result} eq 'Passed'){$Passed++;}    
   if ($TCresult->{result} eq 'Warnings'){$Warnings++;}    
   if ($TCresult->{result} eq 'Failed'){$Failed++;}    
}

print "Passed: $Passed\n";
print "Warnings: $Warnings\n";
print "Failed: $Failed\n";
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Example YAML output

---
dut:
  tc:
    - id: 001.001
      result: Passed
      ts: {}
    - id: 002.001
      result: Failed
      ts: {}
    - id: 003.001
      result: Warnings
      ts: {}
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$VAR1 = [
    {
        'dut' => {
            'tc' => {
                '002.001' => {
                    'ts'     => {},
                    'result' => 'Failed'
                },
                '001.001' => {
                    'ts'     => {},
                    'result' => 'Passed'
                },
                '003.001' => {
                    'ts'     => {},
                    'result' => 'Warnings'
                }
            }
        }
    }
];
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Hello your code works fine but when using my real XML-file somethings goes wrong.

<exec>
  <dut frimware="4.40.1" ipaddress="171.0.0.234" macaddress="00408C727
+B40" model="AXIS 207W" />
  <tc id="001.001" objective="The objective of this test case is to ve
+rify that it is possible to upgrade the DUT's firmware by uploading a
+ firmware image file to the DUT using ftp when the DUT is connected t
+o a network with 100 Mbit/s speed and that the DUT meet the PRS requi
+rement." result="Passed" time="1201248021" version="0.01">
    <ts id="001.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248021" />
    <ts id="001.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248031" />
  </tc>
  <tc id="002.001" objective="The objective is to verify that the DUT 
+can handle the maximum number of events for at least a week" result="
+Failed" time="1201248031" version="0.01">
    <ts id="002.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248031" />
    <ts id="002.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248041" />
  </tc>
  <tc id="004.001" objective="The objective is to verify that the HTTP
+ traffic is marked correctly" result="Passed" time="1201248041" versi
+on="0.01">
    <ts id="004.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248041" />
    <ts id="004.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248051" />
  </tc>
  <tc id="005.001" objective="Verify that the CA certificate can be up
+loaded" result="Passed" time="1201248051" version="0.01">
    <ts id="005.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248051" />
    <ts id="005.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248061" />
  </tc>
  <tc id="006.001" objective="Verify that the DUT can be configured wi
+th the Axis Setup Tool to connect to a wireless network" result="Fail
+ed" time="1201248061" version="0.01">
    <ts id="006.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248061" />
    <ts id="006.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248071" />
  </tc>
  <tc id="007.001" objective="The objective of this test case is to ve
+rify that the DUT is compatible with Axis IP utility" result="Passed"
+ time="1201248071" version="0.01">
    <ts id="007.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248071" />
    <ts id="007.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248081" />
  </tc>
  <tc id="008.001" objective="The objective of this test case is to ve
+rify that the DUT can send live image and that all the links are corr
+ect" result="Passed" time="1201248081" version="0.01">
    <ts id="008.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248081" />
    <ts id="008.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248091" />
  </tc>
  <tc id="009.001" objective="Verify that it is possible to install th
+e AXIS Media Control Embedded (AMC Embedded) on a computer where it h
+as never been installed before" result="Passed" time="1201248091" ver
+sion="0.01">
    <ts id="009.001.001" description="log in using FTP" expected_resul
+t="login granted" result="Passed" time="1201248091" />
    <ts id="009.001.002" description="start upload" expected_result="u
+pload finished" result="Passed" time="1201248101" />
  </tc>
</exec>
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my $tc = $xml->{dut}->[0]->{tc};
foreach my $id (keys %$tc) {
   if ($tc->{$id}->{result} eq 'Passed'){$Passed++;}
   if ($tc->{$id}->{result} eq 'Warnings'){$Warnings++;}
   if ($tc->{$id}->{result} eq 'Failed'){$Failed++;}
}
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Dumping the $xml object with e.g. Data::Dumper helps in such a case.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

So please provide a sample file which actually produces the error.

Perhaps you'll need ForceArray=>['tc'] instead of ForceArray=>1.

Re: A puzzle for parsing XML with XML::Simple! applies to your question. In your case it's the element 'id'.

use XML::Rules;
my %results;
my $parser=XML::Rules->new(
  rules => [
    tc => sub {
      $results{ $_[1]->{result} }++;
      return
    },
    _default => '',
  ],
);
$parser->parse($conf);

foreach my $result (sort keys %results) {
  print "$result: $results{$result}\n";
}
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Why build a structure containing all the data from the XML if all you want to know are the counts of the different result attributes of the <tc> tag?