ksh typeset is not returning value 0 while exiting from a POSIX function

Issue

• ksh typeset is not returning value 0 while exiting from a POSIX function

# cat ./a

#!/bin/ksh
# Sample script to demo ksh typeset problem.
# Set vars to global values...
X="X"
Y="Y"

echo "X = $X"     # value of var X, which should be "X".
echo "Y = $Y"     # value of var Y, which should be "Y".

GG() {          # Define function named GG.
typeset Y       # typeset var Y tobe local value only.
Y="Z"          # Set function GG's var Y to "Z".
echo "X = $X"     # value of var X, which should be "X".
echo "Y = $Y"     # value of var Y, which should be "Z".
}

GG           # Call function GG

echo "X = $X"     # value of var X, which should be "X".
echo "Y = $Y"     # value of var Y, which should be "Y".

• The last line of above script, “Y =” should have value Y, not Z. But its giving "Z" value.

• ksh typeset not  keeping variables local within functions.

• ksh typeset within functions  are changing values of global variables outside of functions.