$[ = 9999;      #This loop doesn't run because @checksThisMonth returns the array size, which is less than 1501.

for ($i = $[;               #initialization list
     $i < @checksThisMonth; #conditional expression
     $i++){                 #increment list

   print "$checksThisMonth[$i]";

}

#This loop runs because $#checksThisMonth returns the last cell index.

for ($i = $[; $i <= $#checksThisMonth; $i++){
    print "$checksThisMonth[$i]";
}