#!/usr/bin/perl
use warnings;
use strict;

use XML::LibXML;

my $text_file = shift;

open my $In, '<', $text_file or die $!;
my $extract = join '\s+(.*?)\s*', qw( FirstName LastName Email BirthDa
+te $ );
$extract = qr/$extract/;
my %birthday;
while (<$In>) {
    my ($first, $last, $email, $bdate) = /$extract/;
    $birthday{$email} = $bdate;
}

while (my $xml_file = shift) {
    my $dom = 'XML::LibXML'->load_xml(location => $xml_file);
    my $email = $dom->findvalue('/contractor/person/email');
    unless (exists $birthday{$email}) {
        warn "No birthday for $email!\n";
        next
    }
    my $person = $dom->find('/contractor/person');
    my $bday = $person->[0]->addChild($dom->createElement('birthday'))
+;
    $bday->appendText($birthday{$email});
    $dom->toFile($xml_file);
}
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See XML::LibXML for documentation.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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An example using XML::Twig

#!/usr/bin/perl
use strict;
use autodie;
use XML::Twig;
use Data::Dumper;
$Data::Dumper::Terse = 1;
use constant DEBUG => 1;

my $base  = 'D:/Some/Specific/Folder';

# birthdate lookup table
my $oldqr = 'c:/temp/oldqr.txt'; 
my $lookup = fetch_birthdates($oldqr);
print '$lookup=',Dumper $lookup if DEBUG;

# process XML files
#my @files  = glob( $base.'/ToUpload/Staging/*' );
my @files  = ('test.xml');
print '@files=',Dumper \@files if DEBUG;
for my $file (@files){
  add_birthdate($file,$lookup);
}

# build birthdate lookup table
sub fetch_birthdates {
  my $infile = shift;
  my %hash = (); my $count = 0;
  open IN,'<',$infile; # autodie
  while (<IN>){
    ++$count; 
    chomp;   
    # old format    
    #if (my @f = /FirstName(.*)LastName(.*)Email(.*)BirthDate(.*)/i){
    # s/^\s+|\s+$//g for @f;      # trim spaces
      my @f = split ';',$_; # new format
      my $pk = join ';',@f[0..2]; # create lookup key
      if (exists $hash{$pk}){ 
        die "ERROR Duplicate record in $infile '$pk' line $count\n";
      } else {
        $hash{$pk} = $f[3];
      }
    #}
  }
  close IN;
  print "$count records read from $infile\n";
  return \%hash;
}

# add birth date from lookup 
# using firstname;name;email as key
sub add_birthdate {
  my ($file,$lookup) = @_;
  my $twig = XML::Twig->new( pretty_print => 'indented' );    
  $twig->parsefile( $file ); 
  my ($person) = $twig->findnodes( 'person' );

  my $pk = join ";",
           $person->findvalue('firstname'),
           $person->findvalue('name'),
           $person->findvalue('email');
   
  print "Reading $file : ";       
  if (exists $lookup->{$pk}){
    my $birthdate = $lookup->{$pk};
    my $node = $person->first_child( 'birthdate' );
    $node->set_text( $birthdate );
    print "$birthdate added for '$pk'\n";
    
    open my $out,'>',$file.'.modified'; #autodie
    $twig->print($out);  
    close $out;
    
  } else {
    print "ERROR - no birthdate for '$pk'\n";
  }
}
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