If you are interested in using an XML parser instead of a regex, XML::Twig can give you the whole element you are looking for: 
use warnings;
use strict;
use XML::Twig;

my $str = '
<DataEnd>
<Dataentry>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
</Dataentry>
<Dataentry>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
</Dataentry>
<Dataentry>
    <Data>aaaaaa</Data>
    <Data>bbbbbb</Data>
    <Data>aaaaaa</Data>
</Dataentry>
<Dataentry>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
    <Data>aaaaaa</Data>
</Dataentry>
</DataEnd>
';

my $t = XML::Twig->new(
    twig_handlers => { Dataentry => \&dentry }
);
$t->parse($str);

sub dentry {
    my ($t, $ent) = @_;
    my $found = 0;
    for my $data ($ent->children('Data')) {
        if ($data->text() eq 'bbbbbb') {
            $found = 1;
            next;
        }
    }
    if ($found) {
        # do something
    }
}

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In reply to Re: Match on line, read backwards to opening xml tag then forward to closing tag by toolic
in thread Match on line, read backwards to opening xml tag then forward to closing tag by shadowfox

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