Created Perl EVENT_ENTERZONE (markdown)

Perl-EVENT_ENTERZONE.md

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+EVENT_ENTERZONE is triggered when a player enters a zone--not to be confused with [Perl EVENT_ZONE](https://github.com/EQEmu/Server/wiki/Perl-EVENT_ZONE), which is triggered when a player LEAVES a zone.  
+
+This event allows you to send the player an emote (like the Wayfarer Brotherhood text), set a compass mark (for an LDON adventure), start timers, check tasks, and a great number of other functions.  
+
+This perl event is most commonly used in the zone's player.pl file, or in the global_player.pl file.
+
+### Triggered
+
+* When a player enters a zone.
+
+### Examples
+
+* In this example, every time someone enters the zone, they will hear the DING! sound that plays when you gain a level.
+
+```perl
+sub EVENT_ENTERZONE {
+     #:: Because it's funny.
+     quest::ding();
+}
+```
+
+* In this example, when a player is part of a Rujarkian Hills Adventure, they will see a mark on their compass. 
+
+```perl
+sub EVENT_ENTERZONE {
+     #:: Create a scalar for storing the instance ID
+     $RujDInstance = quest::GetInstanceID("rujd",50);
+     #:: If the instance ID exists, it should be greater than 0--mark the player's compass if it is
+     if ($RujDInstance > 0) {
+          #:: Create a line on the compass leading the player to X,Y,Z
+          $client->MarkCompassLoc(-157.09, 19.31, 100);
+     }
+}
+```
+
+* In this example, we set the player's 1H Slashing skill (Skill ID 1) to zero if we haven't set it to zero before.
+* We then set a quest global so that we don't zero the skill out the next time the player enters a zone.
+
+```perl
+sub EVENT_ENTERZONE {
+     #:: Check that the 'onehandslashingzerodout' quest global does not exist
+     if (!defined $qglobals{"onehandslashingzerodout"}) {
+          #:: Set the skill ID 1 to value 0
+          $client->SetSkill(1, 0);
+          #:: Set a quest global so that we do not zero the skill on the next zone in
+          quest::setglobal("onehandslashingzerodout", 1, 5, "F");
+     }
+}
+```