我需要你的帮助来学习的xml/文本格式文件提取我的xml/txt文件包含的一个巨大的数据如下所述的格式。

<authorList>
<author>
<fullName>Oliver LA</fullName>
<firstName>L A</firstName>
<lastName>Oliver</lastName>
<initials>LA</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>University of Liverpool, Liverpool, UK. Electronic address: l.oliver@liverpool.ac.uk.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Hutton DP</fullName>
<firstName>D P</firstName>
<lastName>Hutton</lastName>
<initials>DP</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>North West Radiotherapy Operational Delivery Network, The Christie Hospital, Manchester, UK; University of Liverpool, Liverpool, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Hall T</fullName>
<firstName>T</firstName>
<lastName>Hall</lastName>
<initials>T</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>North West Radiotherapy Operational Delivery Network, The Christie Hospital, Manchester, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Cain M</fullName>
<firstName>M</firstName>
<lastName>Cain</lastName>
<initials>M</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>Clatterbridge Cancer Centre, Liverpool, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Bates M</fullName>
<firstName>M</firstName>
<lastName>Bates</lastName>
<initials>M</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>East of England Radiotherapy Network, Norfolk &amp; Norwich University Hospital, Norwich, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Cree A</fullName>
<firstName>A</firstName>
<lastName>Cree</lastName>
<initials>A</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>Clatterbridge Cancer Centre, Liverpool, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
<author>
<fullName>Mullen E</fullName>
<firstName>E</firstName>
<lastName>Mullen</lastName>
<initials>E</initials>
<authorAffiliationDetailsList>
<authorAffiliation>
<affiliation>Clatterbridge Cancer Centre, Liverpool, UK.</affiliation>
</authorAffiliation>
</authorAffiliationDetailsList>
</author>
</authorList>

我需要的输出格式，如电子邮件，名，姓，从属关系和输出应导出到文本文件。
通过使用Perl软件，我开发了下面提到的代码。

#!usr/bin/perl
use strict;
use warnings;
open(FILEHANDLE, "<data.xml")|| die "Can't open";
my @line;
my @affi;

my @lines;
my $ct =1 ;
print "Enter the start position:-";

my $start= <STDIN>;
print "Enter the end position:-";

my $end = <STDIN>;

print "Processing your data...\n";
my $i =0;
my $t =0;
while(<FILEHANDLE>)
{
    if($ct>$end)
    {
       close(FILEHANDLE);
       exit;
       
    }
    if($ct>=$start)
    {
       $lines[$t] = $_;
       $t++;
     }
     
     if($ct == $end)
     {
    my $i = 0;
    my $j = 0;
    my @last;
    my @first;
    my $l = @lines;
    my $s = 0;

while($j<$l)
{
    if ($lines[$j] =~m/@/)
    {
        $line[$i] = $lines[$j];
        $s = $j-3;
        $first[$i]=$lines[$s]; 
        $s--;
        $last[$i] = $lines[$s];
        #$j = $j+3;
        #$last[$i]= $lines[$j];
        #$j++;
        #$first[$i] = $lines[$j];
        $i++;
    }
$j++;
}
my $k = 0;
foreach(@line)
{
  $line[$k] =~ s/<.*>(.* )(.*@.*)<.*>/$2/;
  $affi[$k] = $1;
  $line[$k] = $2;
    $line[$k] =~ s/\.$//;
    
    
    $k++;
  }

my $u = 0;
foreach(@first)
{
  $first[$u] =~s/<firstName>(.*)<.*>/$1/;
  $first[$u]=$l;  
  $u++
  }
my $m = 0;
foreach(@last)
{
  $last[$m] =~s/<lastName>(.*)<.*>/$1/;
  $last[$m] = $1;    
  $m++
  }
my $q=@line;
open(FILE,">RAVI.txt")|| die "can't open";
my $p;

for($p =0; $p<$q; $p++)
{  
  print FILE "$line[$p],$first[$p],$last[$p],$affi[$p]\n";
} 

close(FILE);
     }
     
  
  $ct++;
  }

通过使用此代码，我能够得到输出电子邮件，，姓氏，隶属关系格式。
我无法通过使用给定数据中的代码获得firstName。我是Perl技术的新手。我请求您帮助我修复代码中的错误。提前感谢您。