It is undef. However you're displaying it is stringifying it most likely.

Update: Oops, I stand corrected. Assigning undef in a template does look like it gets an empty string. Interesting. Amended code sample setting baz directly in the template.

Another update: Did some poking and I'm most of the way to convincing myself to agreeing that this might be a bug. It's prossibly worth at least pinging the mailing list with a sample script like this and seeing what the maintainers say.

Update the third: ++ and agreement with those below that relying on results from logic in the display template for anything other than displaying things just raises the hackles. 

#!/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.

[download]

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re^3: Undef value in Template Toolkit by Fletch
in thread Undef value in Template Toolkit by DreamT

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