Hi Mr tibbles
First, beta 18 had a lot of problems. Read thru the last couple pages of the v1.20(pages 37 & 38). install beta 1.20.17a, then look for "19c_final_build.exe". They seem to be the most stable.
To answer your Q, "plrcurrentweapon=0" means "your current weapon from weapon slot 0 (zero). I have a feeling you intended it as not holding/having the lantern? The condition "plrcurrentweapon" one has to name the weapon (plrcurrentweapon=ww2\hand_lantern) or what slot your weapon is using (plrcurrentweapon=1 thru 0).
If your new to scripting try this,
:State=0:FlashLightRange=250
:State=0:FlashLightRed=228
:State=0:FlashLightGreen=204
:State=0:FlashLightBlue=23,State=1
:State=1,KeyPressed=33 1:FlashLight=1,State=2,Sound=AudioBank\Switches\Click.wav
:State=2,KeyPressed=33 0:State=3
:State=3,KeyPressed=33 1:FlashLight=0,State=4,Sound=AudioBank\Switches\Click.wav
:State=4,KeyPressed=33 0:State=1
Place it into a trigger zone, use the "F" key to turn on/off the light. Adjust the range & colors to your liking. Also grab a copy of the FPSC Official Community guide. It is a big help for scripting & also the latest script syntax list here..
http://forum.thegamecreators.com/?m=forum_view&t=180924&b=23
best luck