with

@stack = ( ['cfif', 'bool eq "true"'],
           ['cfelse']
         );
[download]

the subs could start with something like

sub start {
 return if $stack[-1][0] eq 'cfif' and $tag ne 'cfelse' and not istrue
+($stack[-1][1]);
 return if $stack[-1][0] eq 'cfelse' and istrue($stack[-2][1]);
}
sub end {
 return if $stack[-1][0] eq 'cfif' and $tag ne 'cfif' and not istrue(.
+..);
 return if $stack[-1][0] eq 'cfelse' and istrue(...);
}
sub text {
 something like what i used in start()
}
[download]

This piece of pseudo-code doesn't handle nested cfif's, but nothing is impossible. Maybe the bool eq "true" syntax is too hard for HTML::Parser, but nesting and ignoring will of course be up to you, just like when you use your own parser.

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
[download]