<?xml version="1.0" encoding="utf-8"?>
<items>
  <find-spot id="12" nr="8" lnr="21" >
    <token1>bla</token1>
    <token2>blu</token2>
    <environment>blub</environment>
  </find-spot>
  <find-spot id="13" nr="8" lnr="21" >
    <token1>bla2</token1>
    <token2>blu2</token2>
    <environment>blub2</environment>
  </find-spot>
</items>

use strict;
use warnings;
use XML::LibXML;

my $parser = XML::LibXML->new();
my $doc = $parser->parse_file("xml.xml");
my @nodes = $doc->findnodes('/items/find-spot');
my $i = 0;
my @blocks = do { local $/ = "\n______________\n"; <DATA> };
for my $node (@nodes) {
    my $block = $blocks[$i];
    my ($header, @lines) = split /\n/, $block;
    pop @lines;
    for my $line (@lines) {
        my $child = $node->addNewChild( "", "environment" );
        $child->appendText("$line");
    }
    $i++;
}
my $docstring = $doc->toString();
print "Neues XML: $docstring\n";
__DATA__
Block 1:
perl1
perl2
perl3
______________
Block 2:
bla
etc.
______________