Thanks, despite being marked "experimental" it does appear to work in the OP's case:

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

my $xml = <<'ENDXML';
<foo xmlns="http://www.example.com"><bar/></foo>
ENDXML

my $reader = XML::LibXML::Reader->new(string => $xml);
while ($reader->read) {
    my $node = $reader->copyCurrentNode;
    $node->setNamespaceDeclURI(undef, undef)
        if $node->nodeName eq 'bar';
    print "$node";
}

__END__

<foo xmlns="http://www.example.com"/><bar/><foo xmlns="http://www.exam
+ple.com"/>
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Unfortunately I might still be missing something, because applied to choroba's code here it doesn't seem to change the namespace of the nodes.

I don't get it. I experimented with $node->setNamespace(undef, undef, 1) which seems to be the simplest namespace handling fucntion, but I couldn't get it work.

XML::LibXML defines setNamespace in the following way:

sub setNamespace {
    my $self = shift;
    my $n = $self->nodeName;
    if ( $self->_setNamespace(@_) ){
        if ( scalar @_ < 3 || $_[2] == 1 ){
            $self->setNodeName( $n );
        }
        return 1;
    }
    return 0;
}
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where _setNamespace comes from its XS component, the important part (I guess) is the following:

       if ( nsPrefix == NULL && nsURI == NULL ) {
            /* special case: empty namespace */
            if ( (ns = xmlSearchNs(node->doc, node, NULL)) &&
                 ( ns->href && xmlStrlen( ns->href ) != 0 ) ) {
                /* won't take it */
                RETVAL = 0;
            } else if ( flag ) {
                /* no namespace */
                xmlSetNs(node, NULL);
                RETVAL = 1;
            } else {
                RETVAL = 0;
            }
        }
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setNamespace returns 1, so I guess it goes the "else if" branch, but the namespace isn't removed from the node. xmlSetNs comes from libxml2 and is defined as (debugging ifdefs removed)

void
xmlSetNs(xmlNodePtr node, xmlNsPtr ns) {
    if (node == NULL) {
    return;
    }
    if ((node->type == XML_ELEMENT_NODE) ||
        (node->type == XML_ATTRIBUTE_NODE))
    node->ns = ns;
}
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Anyone can explain why the namespace isn't changed?

($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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Anyone can explain why the namespace isn't changed?

Hi,

Its some kind of bug, if I were setup to compile libxml2 I'd narrow it down with this addition to LibXML.xs

int
_setNamespaceNULL(self )
        SV * self
    PREINIT:
        xmlNodePtr node = PmmSvNode(self);
    INIT:
        if ( node == NULL ) {
            croak( "lost node" );
        }
    CODE:
        xmlSetNs(node, NULL);
        RETVAL = 1;
    OUTPUT:
        RETVAL
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