I just downloaded clawsker 1.3.1 on openSUSE Leap 15.0 and built it. When it tries to display the version, either in the GUI or on the command line, instead of displaying an actual version number it displays the string @VERSION@
$ ./clawsker -v
Clawsker :: A Claws Mail Tweaker
Perl-GLib version 1.326, built for 2.54.3, running with 2.54.3.
Perl-GTK3 version 0.034, built for 30, running with 3.22.30.
Claws Mail returned version 184.108.40.206.
In the given example you're running the git version not the built version.
After running "make", you should install it somewhere with "make install", as explained in the README.
The built script is available in the "build" subdirectory, the source is not modified at all. Nevertheless you can still check version before installing by running "perl build/clawsker -v".
Ah, thanks. Sorry for the noise.