Cant check empty string

Hello

So i have that script collection, in which i have a single script to create a configuration file.
In there, i have multiple occourences of something like this:

	prj_title=$(tui-read "What is the TITLE? ($prj_name):")
	[[ -z "$prj_title" ]] && prj_title="${prj_name/_/ }"

They all work as expected, if nothing is entred, it fills the variable with the default value.

However, for this it fails, and i fail to figure out why:

#
# Ask for a value, if value is empty, fill it with default
#

prj_tempdird="/tmp/${prj_name}_$ARCH"
prj_tempdir=""

#prj_tempdir=$(tui-read "What is the temp directory? ($prj_tempdird):")
read -p "What is the temp directory? ($prj_tempdird):" prj_tempdir

[[ -z "$prj_tempdir" ]] && prj_tempdir="$tempdird"
[[ -z $prj_tempdir ]] && prj_tempdir="$tempdird"
[[ "" = "$prj_tempdir" ]] && prj_tempdir="$tempdird"
[[ "" = "$(echo $prj_tempdir)" ]] && prj_tempdir="$tempdird"
[[ "" = "$(echo $prj_tempdir|tr -d [[:space:]])" ]] && prj_tempdir="$tempdird"
[[ -z "$(echo $prj_tempdir)" ]] && prj_tempdir="$tempdird"

echo "$prj_tempdir =! $prj_tempdird"

This is what i get:

:) ~ $ sh file1.txt
What is the temp directory? (/tmp/_):/home/TEMP
/home/TEMP =! /tmp/_               (this is 'expected')

+ ~ $ sh file1.txt
What is the temp directory? (/tmp/_):
 =! /tmp/_                        (this is NOT)
+ ~ $ 

This is what i expect:

+ ~ $ sh file1.txt
What is the temp directory? (/tmp/_):
/tmp/_ =! /tmp/_

Any ideas please?
Thank you in advance

How about using prj_tempdird in all your tests?

Argh lol... yes.
Too close too see the image...

Well understood, but what are you using to fill it with in your code snippet?

I dont understand this question.
Guess you posted before my edit?

Yes. That's why noone should edit texts once posted.