Polymorph Macro Question

Hi folks,

I was looking at the PVP macro sticky and was hoping I could just clarify something about the Polymorph Macro.

What does the macro below do?

Here is what I think,

shows the poly tooltip
puts the elemental on passive so it doesn't do anything silly
clears my focus if my current focus is dead - not sure on the second part of line 3??
makes my current target my focus
cast polymorph on my target or if i hold down the shift key on my focus
no idea what the nomod:shift line is for??
stops the macro if i'm not in a group
and if i'm in a group tells the party i'm trying to polymorph something

#showtooltip
/petpassive
/clearfocus [target=focus,dead][target=focus,noexists]
/focus [target=focus,noexists]
/cast [mod:shift, target=focus] Polymorph;
/cast [nomod:shift] Polymorph
/stopmacro [nogroup}
/p !! Sheeping “%T”

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and finally
can i add a line to the above macro to raid mark whatever I just turned into a monkey?

thanks in advance

Bargle the not so famous

It casts polymorph, on your focus if you hold shift and on your target if you don't hold shift....