is %%GECKO%% defined anywhere?

[Anton Shterenlikht]

# cat /usr/ports/textproc/urlview/files/gecko.sh.in 
#! /bin/sh
# $FreeBSD: ports/textproc/urlview/files/gecko.sh.in,v 1.1 2009/11/29 08:24:50 obrien Exp $
# Launch %%GECKO%% for urlview
URL=$@
%%GECKO%% -remote "openurl($URL, new-tab)" || %%GECKO%% $URL
# 

which on installation turns into

# cat /usr/local/bin/gecko.sh 
#! /bin/sh
# $FreeBSD: ports/textproc/urlview/files/gecko.sh.in,v 1.1 2009/11/29 08:24:50 obrien Exp $
# Launch  for urlview
URL=$@
 -remote "openurl($URL, new-tab)" ||  $URL
# 

I cannot find any reference to %%GECKO%% in Mk/*

Please advise

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 331 5944
Fax: +44 (0)117 929 4423