Ok in that case, which ones are considered to be system calls? is it only the system(..) calls or it is any call to underlying c routines also? Like can a call to print FH "foo"; cause ENOMEM? or can an array allocation cause an ENOMEM? so which all statements in the code should be checked for $! ? Here's an example:

@arr = ('x', 'y', 'z');
# error occurs so $! is set. But thinking that this small piece of cod
+e wont cause any error I dont check for $! here.
#some more code her
print join(',', @arr);

open(FILE, "<file.txt") || die (".....error");
# check for $! here
if ($!)
{
# whcih is the culprit line causing this error? is it array allocation
+, or is it print or is it open?
}
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