If I'm reading this right, it looks like the tests for param{'then'} and param{'else'} should always fail and line 172 should never be executed since both of those params were removed at lines 152 and 153.

From trunk/core/lib/Foswiki/Template.pm@7682

147	sub tmplP {
148	    my ( $this, $params ) = @_;
149	
150	    my $template = $params->remove('_DEFAULT') || '';
151	    my $context  = $params->remove('context');
152	    my $then     = $params->remove('then');
153	    my $else     = $params->remove('else');
154	    if ($context) {
155	        $template = $then if defined($then);
156	        foreach my $id ( split( /\,\s*/, $context ) ) {
157	            unless ( $this->{session}->{context}->{$id} ) {
158	                $template = ( $else || '' );
159	                last;
160	            }
161	        }
162	    }
163	
164	    return '' unless $template;
165	
166	    my $val = '';
167	    if ( exists( $this->{VARS}->{$template} ) ) {
168	        $val = $this->{VARS}->{$template};
169	        $val = "$val" if (TRACE);
170	        foreach my $p ( keys %$params ) {
171	            if ( $p eq 'then' || $p eq 'else' ) {
172	                $val =~ s/%$p%/$this->expandTemplate($1)/ge;
173	            }
174	            elsif ( defined( $params->{$p} ) ) {
175	                $val =~ s/%$p%/$params->{$p}/ge;
176	            }
177	        }
178	        $val =~ s/%TMPL:PREV%/%TMPL:P{"$template:_PREV"}%/g;
179	        $val =~ s/%TMPL:P{(.*?)}%/$this->expandTemplate($1)/ge;
180	    }
181	
182	    return $val;
183	}

-- BryanThale - 20 Jun 2010

Yeah, dunno where that came from. then and else are special - they are selected between based on the result of the context test - and in no circumstances should %then% of %else% need to be expanded in the template body.

-- CrawfordCurrie - 28 Jun 2010