for my $para ( $root->children('para') ) {
       if ( $para->first_child_matches('get_this') ) {
            print $para->first_child('get_this')->att('value');
       }
}

##</code><code>##

use strict;
use warnings;

use XML::Twig;
my $xml = <<XML;
<root>
<para id="000">0000000000000000000000000000000000000000000<yahoo>XXXXXXX </yahoo>
   <get_this value="yes" />
   <get_this_two>ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ</get_this_two>
</para>
<para id="111">1111111111111111111111111111111111111111111</para>
<para id="222">2222222222222222222222222222222222222222222</para>
<para id="333">3333333333333333333333333333333333333333333</para>
<para id="444">4444444444444444444444444444444444444444444</para>
<para id="555">5555555555555555555555555555555555555555555</para>

<para_type type="para type 3rd" active="true">
    <para_cat type="category 3" />
</para_type>

<para_type type="para type 2nd" active="false">
    <para_cat type="category 2" />
</para_type>

<para id="XXX" value="XXX_para" >
               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    <para_2nd value="PPPP" />
    <para_3rd>
         <para_3rd_name value="para type 3rd" active="true">
              <para_4th value="empty" active="false"/>
         </para_3rd_name>
    </para_3rd>
    <para_4th value="on" eff="no">does this work</para_4th>
</para>
</root>
XML

my $tmp = XML::Twig->new();
$tmp->parse ($xml);
my $root = $tmp->root;

print "Here is XML file \n" . $xml . "\n";
print ">>>>>>>>>> children of when 'para' is root<<<<<<<<<<<<<\n";
print $_->trimmed_text (), "\n" for $root->children ('para');
print ">>>>>>>>>> first_child of when 'para' is root <<<<<<<<<<<<<\n";
print $_->text (), "\n" for $root->first_child ('para');
print ">>>>>>>>>> last_child of when 'para' is root <<<<<<<<<<<<<\n";
print $_->text (), "\n" for $root->last_child('para');
print ">>>>>>>>>> children of when 'para_4th' is root<<<<<<<<<<<<<<<\n";
print $_->text (), "\n" for $root->last_child('para')->first_child('para_4th');
print ">>>>>>>>>> find att 'eff' value from para_4th <<<<<<<<<<<<<\n";
print $_,   "\n" for $root->last_child('para')->first_child('para_4th')->att('eff');

print ">>>>>>>>>> children of when 'para' is root find value of id<<<<<<<<<<<<<<<<<<\n";
#print $_,   "\n" for $root->children('para')->att('id');
for my $para ( $root->children('para') ) {
       print $para->att('id') . "\n";
}

for my $para ( $root->children('para') ) {
       if ( $para->first_child_matches('get_this') ) {
            print $para->first_child('get_this')->att('value');
       }
}


##</code><code>##

Here is XML file 
<root>
<para id="000">0000000000000000000000000000000000000000000<yahoo>XXXXXXX </yahoo>
   <get_this value="yes" />
   <get_this_two>ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ</get_this_two>
</para>
<para id="111">1111111111111111111111111111111111111111111</para>
<para id="222">2222222222222222222222222222222222222222222</para>
<para id="333">3333333333333333333333333333333333333333333</para>
<para id="444">4444444444444444444444444444444444444444444</para>
<para id="555">5555555555555555555555555555555555555555555</para>

<para_type type="para type 3rd" active="true">
    <para_cat type="category 3" />
</para_type>

<para_type type="para type 2nd" active="false">
    <para_cat type="category 2" />
</para_type>

<para id="XXX" value="XXX_para" >
               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    <para_2nd value="PPPP" />
    <para_3rd>
         <para_3rd_name value="para type 3rd" active="true">
              <para_4th value="empty" active="false"/>
         </para_3rd_name>
    </para_3rd>
    <para_4th value="on" eff="no">does this work</para_4th>
</para>
</root>

>>>>>>>>>> children of when 'para' is root<<<<<<<<<<<<<
0000000000000000000000000000000000000000000XXXXXXX ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
1111111111111111111111111111111111111111111
2222222222222222222222222222222222222222222
3333333333333333333333333333333333333333333
4444444444444444444444444444444444444444444
5555555555555555555555555555555555555555555
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX does this work
>>>>>>>>>> first_child of when 'para' is root <<<<<<<<<<<<<
0000000000000000000000000000000000000000000XXXXXXX ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
>>>>>>>>>> last_child of when 'para' is root <<<<<<<<<<<<<

               XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    does this work
>>>>>>>>>> children of when 'para_4th' is root<<<<<<<<<<<<<<<
does this work
>>>>>>>>>> find att 'eff' value from para_4th <<<<<<<<<<<<<
no
>>>>>>>>>> children of when 'para' is root find value of id<<<<<<<<<<<<<<<<<<
000
111
222
333
444
555
XXX