#!/usr/bin/env perl
use strict;
use warnings;

use Template ();

my $t = Template->new( {} );

my $tmpl_source = <<"EOT";
This is my template.
[% timestamp %]
[%- IF foo.defined %]
foo is defined and is "[% foo %]"
[%- ELSE %]
foo is undef
[%- END %]
[%- IF bar.defined %]
bar is defined and is "[% bar %]"
[%- ELSE %]
bar is undef
[%- END %]
[%- baz = undef -%]
[%- IF baz.defined %]
baz is defined and is "[% baz %]"
[%- ELSE %]
baz is undef
[%- END %]
Done.
EOT

$t->process( \$tmpl_source, { foo => undef,
							 bar => q{},
							 timestamp => scalar localtime() } )
  or die $t->error, qq{\n};

exit 0;

__END__
$ perl tt_test.plx
This is my template.
Tue Aug 20 11:07:30 2019
foo is undef
bar is defined and is ""
baz is defined and is ""
Done.