my $tmpl = "";
my $item = "CONTINUE";

if ($item eq "SELECT") {
    $tmpl  = "select.tmpl";
} elsif ($item eq "CONTINUE") {
    $tmpl  = "continue.tmpl";
} elsif ($item eq "DENIED"){
    $tmpl  = "denied.tmpl";
}
my $template = HTML::Template->new( filename => $tmpl );

##</code><code>##

# template.tmpl
<TMPL_VAR NAME="function_xyz">

# Perl:
my $tmpl = HTML::Template->new( filename => 'template.tmpl' );
my @all_params = $tmpl->param();

foreach (@all_params) {
    if ($_ =~ /^function_/i) {
        my ($a,$b) = split (/_/,$_,2);
        $tmpl->param($_	=> $b() );
    }
}

sub xyz {
 return "template value needed";
}