use Template;

my $t = Template->new(
   INCLUDE_PATH => '.',
   PRE_PROCESS  => 'main.tmpl'
) or die $!;

open my $fh, '<', 'index.tmpl' or die $!;
my $template = do { local $/; <$fh> };
close $fh;

while ( sleep 1 ) {
   $t->process(\$template) or die $!;
}