Hi
<TMPL_IF foo><TMPL_INCLUDE foo.txt>
</TMPL_IF>Hello

##</code><code>##

Hi
\
<TMPL_IF foo>\
<TMPL_INCLUDE foo.txt>
</TMPL_IF>\
\
Hello

##</code><code>##

  ... $in =~ s/\\\n[\t ]*//g; ...