@Falk David (filedescriptor), thank you for confirming my suspicions.

Just adding some potentetially useful/useless information here:

Jean First, yours is not exactly a control experiment. You're using an experimental build (2.81) but more importantly testing on a different model iMac with the AMD Radeon R9 M370X, which has twice the RAM (2GB) of the Radeon HD 5750 (1GB).
Further experiments with procedural materials on this model iMac lead me to believe that Blender 2.8 requires minimum a 2GB video card, as after a certain point in the node chain (I have not yet documented where exactly) Blender 2.8 crashes in LookDev/EEVEE but not in Cycles/Rendered.

After trying to create another procedural texture, in LookDev/EEVEE Blender crashes. I suspect it's not a bug per se but possibly my iMac Mid-2010 (not exactly cutting-edge hardware any more). Again, while working in Cycles/Rendered everything works as expected. Attached is the crash log and the .blend file.

@Germano Cavalcante (mano-wii) it's most likely the same bug because as @rafael suarez ziegelmaier (rafazig) states

@William Reynish (billreynish) once again you have nailed it! Mapping the key left of 1 (in my case, backslash) is the obvious and most elegant solution in my opinion.

@Paul Kotelevets (1D_Inc) ...
Seriously, Paul? "Comfortable peripherals?" "...Mac or comfortable work?" I came here looking to inform/remind the developers about this shortcoming regarding the backtick key and I have to hear this kind of nonsense? I'm not talking about an Amiga, Sun, Wang, Atari or Be keyboard. It's a Macintosh keyboard and whether you personally like it or not its a widely-accepted layout. Macintosh Blender users (regardless of keyboard layout) are more than a bump on the map and I'm confident the developers/Blender Foundation can confirm this. 2.8 is the first version that actually has the Command key mapped.

@Paul Melis (paulmelis) sto guardando la mia tastiera Mac italiano...e non trovo il tasto della tilde...perché non c'è! Per favore, come l'hai risolto?