Passing additional arguments to XML::Twig handlers

[pseudomonas]

Wise Monks: I'm using XML::Twig and its function handlers. These take coderefs, to which are passed (as @_) the values of the twig and the section being processed. However, if I want to pass the coderef other values as well, it doesn't seem to retrieve the twig and section as I'd expect. I'm a bit stumped, I can't seem to find this case in the documentation. Example:

#!/usr/bin/perl
use XML::Twig;
my $t=XML::Twig->new( twig_handlers => { name => \&my_s });
$t->parse('<doc><name>Alice</name><name>Bob</name></doc>');

sub my_s {
    my ($twig, $section, $greeting) = @_;
    print $greeting || "Hello" , ", ", $section->text(), "!\n";
}

# Yields:
# Hello, Alice!
# Hello, Bob!

If I try

my $t=XML::Twig->new( twig_handlers => { name => \&my_s("Hi") });
# Can't call method "text" on an undefined value
# likewise with &my_s->("Hi")

What am I missing?

[Fletch]

Use an anonymous coderef (which adds the extra arguments) to set the handler.

my $t = XML::Twig->new( twig_handlers => { name => sub { my_s( @_, "Hi
+" ) } } );

[pseudomonas]

Thanks! This seems to work fine.

[mirod]

The best explanation I have seen about closures and how to use them in XML::Twig is Simon Cozens' Achieving Closure.

[moritz]

If you want only constant args, you can fall back on closures:

my $greeting = "hi";

my $my_s = sub {
    my ($twig, $section) = @_;
    print $greeting || "Hello" , ", ", $section->text(), "!\n";
}

You can then pass the closure in $my_s just like a normal reference to a sub.

[pseudomonas]

The args change from parse to parse, unfortunately. Closures are something I need to get more used to in general, though - thanks!