How do you make it so an Enter() proc will change a variable on a player (I having Enter(mob/M))

but I can't get it to work like other things only having to put usr or src or attacker ect. but now I do not know what to put in front of the .variable = blah

in other cases I would put for example
attacker.variable = blah
but in this code I do not know what to put
here it is:
turf/grass
icon = 'grass.dmi'
Enter(mob/M)
pl = 114

please help
and thanks in advance