Different behaviour of 'stat' function after assignment to $! (errno).

[muxxum]

Hello,

I was wondering if anyone can explain the difference between the outputs of two following programs. The only difference between the programs is that 0 is assigned to $! in the second program.

Program 1:

stat("non_existing_file");
die "died at first stat" if -$!;
stat("non_existing_file");
die "died at second stat" if -$!;

Output:

died at first stat at a.pl line 3.

Program 2:

$! = 0;
stat("non_existing_file");
die "died at first stat" if -$!;
stat("non_existing_file");
die "died at second stat" if -$!;

Output:

died at second stat at a.pl line 5.

If 0 is assigned to $! before the first stat, the first failed stat does not set the $!.

I also noticed that if instead of $!=0 we do a undef $!, the program behaves as the first one.

Thanks!