in reply to Re^3: language selection via libxml
in thread language selection via libxml

With the quotes I get 
Scalar found where operator expected near ""/language/$language/widget
+[\@ID="$id"

String found where operator expected near "$id"]""

syntax error near ""/language/$language/widget[\@ID="$id"

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Update: Perhaps I should have said "lose double quotes around $id", though no quotes works for me too: 
"/language/$language/widget[\@ID="$id"]"  - Error
"/language/$language/widget[\@ID='$id']"  - OK
"/language/$language/widget[\@ID=$id]"    - OK

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Re^5: language selection via libxml
by choroba (Cardinal) on Jan 20, 2014 at 13:09 UTC 
    "/language/$language/widget[\@ID=$id]"    - OK

    [download]
    Well, it is a valid syntax, but the meaning is different: it tries to find a widget whose ID attribute has the same value as the text of the child of widget whose name is $id. Barewords are not promoted to strings in XPath.
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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[d/l]
[select]
      I am trying to get this as I believe Xpath expressions to be very powerful and I've always had a hard time understanding them.

      The two examples marked OK above seem to behave the same way: 

      use XML::LibXML;
my $tree = XML::LibXML->load_xml(string => <<'EOT');
<?xml version="1.0"?>
<language>
    <english>
        <widget ID="1">input</widget>
        <widget ID="2">output</widget>
    </english>
    <deutsch>
        <widget ID="1">eingabe</widget>
        <widget ID="2">ausgabe</widget>
    </deutsch>
</language>
EOT

test('english',1);
test('deutsch',1);

sub test {
    my ($language,$id) = @_;
    my @result=$tree->findnodes("/language/$language/widget[\@ID=$id]"
+);
    print $_->textContent . "\n" for @result;
    my @result2=$tree->findnodes("/language/$language/widget[\@ID='$id
+']");
    print $_->textContent . "\n" for @result2;
}

      [download]
      Output: 
      input
input
eingabe
eingabe

      [download]
[reply]
[d/l]
[select]
        OK, numbers do not have to be enclosed in quotes, and a valid identifier cannot start with a digit. Try using "a" and "b" as the identifiers, though.
        لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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Re^5: language selection via libxml
by hdb (Monsignor) on Jan 20, 2014 at 12:52 UTC

    You need to escape the quotes as well or use single quotes around your string: 

    $result=$tree->findnodes('/language/$language/widget[@ID="$id"]');

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[d/l]
      Using your example I get: 
      XPath error : Invalid expression
/language/$language/widget[@ID="$id"]
          ^

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[reply]
[d/l]

        I had not seen the variable in between, sorry. You could do 

        $result=$tree->findnodes('/language/'.$language.'/widget[@ID="$id"]');

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[d/l]

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