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Perl Recipe of the Day

The following recipe is from Perl Cookbook, 2nd Edition, by Tom Christiansen and Nathan Torkington. All links in this recipe point to the online version of the book on the Safari Bookshelf.

Buy it now, or read it online on the Safari Bookshelf.

21.5. Interrogating Headers

21.5.1. Problem

You want to learn the value of a header sent by the client.

21.5.2. Solution

Use the $r->header_in method:

$value = $r->header_in("Header-name");

21.5.3. Discussion

For example, suppose you want to discover the client's preferred language (as sent in the Accept-Language header).

if ($r->header_in("Accept-Language") !~ /\ben-US\b/i) {
  $r->print("No furriners!");
  return OK;
}

If you want to access more than one header, use the $r->headers_in method, which returns a list of key-value pairs of all clients' request headers, which are typically assigned to a hash:

%h = $r->headers_in;
if ($h{"Accept-Language"} !~ /\ben-US\b/i) {
  $r->print("No furriners!");
  return OK;
}

21.5.4. See Also

Writing Apache Modules with Perl and C; Recipe 3.4 in mod_perl Developer's Cookbook; the Apache.pm manpage