I suppose you're talking about Perl as a server scripting language, delivering WML-pages to WAP enabled devices.

Since it is just a question af MIME-types and content-types to determine what's WML and what not (and what the server serves), one just has to add the correct MIME-Type to the server conf and output pure WML. (Ok, right now, there's no CGI.pm with WAP support, but who knows?)

Add these MIME-types:

AddType text/vnd.wap.wml .wml
AddType image/vnd.wap.wbmp .wbmp
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to your server conf.

And this would be a small CGI WAP example:

#!/usr/bin/perl -w

use CGI qw(:standard);
use strict;

my $q = new CGI;

# This determines being WML or not.
print header(-type => 'text/vnd.wap.wml');
print "<?xml version=\"1.0\"?>\n";
print "<!DOCTYPE wml PUBLIC \"-//WAPFORUM//DTD WML 1.1//EN\" \"http://
+www.wapforum.org/DTD/wml_1.1.xml\">";

# This is the actual WML content.
print "<wml>\n";
print "<card id=\"main\" title=\"Hello World\">\n";
print "<p>Hello, " . $q->param("f") . " " . $q->param("l") . "!</p>\n"
+;
print "</card>\n";
print "</wml>\n";
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Update: Just saw ar0n's post, didn't know there's a CGI::WML module. Nice. (But to be honest: who needs WAP anyway?)