SQR Procedure parameters/arguments - peoplesoft

Question

I'm trying to understand more about how arguments/parameters are used when calling and executing procedures. I understand that procedures that contain an parameter with a leading colon (:) pass back values to the calling DO command, however I think what it a little confusing is it appears that the variables names from what the calling DO command issues, and what the procedure (called by DO) returns don't necessarily have to be the same name. If someone could help shed some light on the following examples and explain what values are being either passed to/from or how their referenced by the issuing DO command that would be helpful.
It looks like the call to run the Get-Recursive-Reports-To (do Get-Recursive-Reports-To($Recursive_Line, $_POSITION_NBR, #_Global_Counter) is issuing these 3 variables as parameters to the procedure Get-Recursive-Reports-To, however as I look through the Get-Recursive-Reports-To procedure, I do not see any references of the variable $Recursive_Line within this procedure, so is the procedure actually using it or what is the purpose of including it? Similar question with $_val_Position_NBR, where is this variable getting it's value assigned from?
And then within the Get-Recursive-Reports-To procedure I see a parameter - :$var_Next_EMPLID that I believe is being passed back to the calling DO in the Run-Recursion procedure, but I can not figure out how/where it uses the value passed back to it...
begin-procedure Run-Recursion
let #_Global_Counter = 0
let $Recursive_Line = ''
let $Data_Line_EMPL = ''
let $Data_Line_EMPL = $_BUSINESS_UNIT || '|' || $_BUSINESS_UNIT_DESCR || '|' || '2019' || '|' ||
$_EMPLID || '|' || $_NAME || '|' || $_DEPTID || '|' || $_DEPT_DECSR || '|' || $_JOBCODE || '|'
do Get-Recursive-Reports-To($Recursive_Line, $_POSITION_NBR, #_Global_Counter)
let $Data_Line_EMPL = $Data_Line_EMPL || $Recursive_Line
do Write-Data-Line($Data_Line_EMPL)
end-procedure
begin-procedure Get-Recursive-Reports-To(:$val_Data_Line, $val_Current_Position_Nbr, #Recursion_Counter)
let #Recursion_Counter = #Recursion_Counter + 1
do Get-the-ReportsTo-for-the-Current-Position($val_Current_Position_Nbr, $Next_Position_Nbr, $Next_EMPLID)
do Check-For-Stop($Stop_Recursion, $val_Current_Position_Nbr, $Next_Position_Nbr, #Recursion_Counter)
if $Stop_Recursion = 'N'
let $val_Data_Line = $val_Data_Line || $Next_EMPLID || '|'
do Get-Recursive-Reports-To($val_Data_Line, $Next_Position_Nbr, #Recursion_Counter)
end-if
end-procedure
begin-procedure Get-the-ReportsTo-for-the-Current-Position($_val_Position_NBR, :$var_ReportsTo, :$var_Next_EMPLID)
let #local_counter = 0
begin-select
G.REPORTS_TO &G.Reports_to
let $var_ReportsTo= &G.Reports_To
from PS_POSITION_DATA G
WHERE G.POSITION_NBR = $_val_Position_NBR
and G.EFF_STATUS = 'A'
AND (G.EFFDT =
(SELECT MAX(G_ED.EFFDT) FROM PS_POSITION_DATA G_ED
WHERE G.POSITION_NBR = G_ED.POSITION_NBR
AND G_ED.EFFDT <= $_As_OF_Date))
end-select
begin-select
H.EMPLID &H.EMPLID
Z.NAME &Z.NAME
let $var_Next_EMPLID= &H.EMPLID
let #local_counter = #local_counter + 1
from PS_JOB H !, PS_EMPLOYEES Z
WHERE H.POSITION_NBR = $var_ReportsTo
and H.EMPL_STATUS not in ('D', 'R', 'T')
and (H.EFFDT =
(SELECT MAX(H_ED.EFFDT) FROM PS_JOB H_ED
WHERE H.EMPLID = H_ED.EMPLID
AND H.EMPL_RCD = H_ED.EMPL_RCD
AND H_ED.EFFDT <= $_As_Of_Date))
end-select
if #local_counter > 1
let $var_Next_EMPLID = $local_counter || ' ' || 'Employees in this Position'
end-if
if #local_counter = 0
let $var_Next_EMPLID = 'Position Vacant'
end-if
end-procedure

Answer 1

The FIRST call to Get-Recursive-Reports-To from the main procedure uses the $Recursive_Line variable. It doesn't have to be referenced again because it's internal to the procedure.
Once IN procedure Get-Recursive-Reports-To, the name of this variable becomes $val_Data_Line and is used to call back to the same procedure Get-Recursive-Reports-To which can change it. I guess ergo the name, Get-Recursive-Reports-To.
Recursion is a pain in the neck but it looks like it's being used to go up an organizational chain, finding the reports to employee id, then getting the name of that person.
Variable $var_Next_EMPLID is passed from Get-the-ReportsTo-for-the-Current-Position back to the caller as variable $Next_Emplid which is then used again to call Get-Recursive-Reports-To.
I can't tell when or why the Recursion stops since you didn't include the procedure "Check-For-Stop". Looks like there is some check - perhaps if the $Val_Current_Position_Nbr or $Next_Position_Nbr is blank or equal or something.