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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