XML::Twig is much easier on the noggin

{
    use strict; use warnings;
    use Data::Dump qw/ dd /;
    use XML::Twig ;
    my( %os, @amk );
    XML::Twig->new(
      twig_handlers => {
#~         '/Outpatient_Services/Outpatient_Service/Outpatient_Clinic/
+AM_Key' => sub {
        'AM_Key' => sub {
          print $_->xpath, "\n";
          push @amk, $_->trimmed_text;
        },
        'Outpatient_Service' => sub {
          print $_->xpath, "\n";
          $os{ shift @amk }++ while @amk;
        },
      },
    )->xparse( 'pm1002448.xml' );
    
    my $ref = {
        Outpatient_Services => \%os,
    };
    dd $ref; use YAML(); print YAML::Dump( $ref);
}
__END__
/Outpatient_Services/Outpatient_Service/Outpatient_Clinic/AM_Key
/Outpatient_Services/Outpatient_Service
/Outpatient_Services/Outpatient_Service[2]/Outpatient_Clinic/AM_Key
/Outpatient_Services/Outpatient_Service[2]
/Outpatient_Services/Outpatient_Service[3]/Outpatient_Clinic/AM_Key
/Outpatient_Services/Outpatient_Service[3]
/Outpatient_Services/Outpatient_Service[4]
/Outpatient_Services/Outpatient_Service[5]/Outpatient_Clinic/AM_Key
/Outpatient_Services/Outpatient_Service[5]
/Outpatient_Services/Outpatient_Service[6]
{ Outpatient_Services => { AM01 => 2, AM02 => 1, AM04 => 1 } }
---
Outpatient_Services:
  AM01: 2
  AM02: 1
  AM04: 1
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