Question

I have a Perl subroutine which updates an RSS feed. I want to test the returned value, but the function is used in many places so I wanted to just test the default variable $_ which as far as I understand should be the assigned the return value if no variable is specified.

The code is a bit too long to include all of it, but in essence it does the following

sub updateFeed {
  #....
  if($error) {
    return 0;
  }
  return 1;
}

Why then does

$rtn = updateFeed("My message");
if ($rtn < 1) { &Log("updateFeed Failed with error $rtn"); }

NOT log any error

whereas

updateFeed("myMessage");
if ($_ < 1) { &Log("updateFeed Failed with error $_"); }

logs an error of “updateFeed Failed with error“? (Note no value at the end of the message.)

Can anyone tell me why the default variable seems to contain an empty string or undef?

Answer 1

Because Perl doesn’t work that way. $_ doesn’t automatically get the result of functions called in void context. There are some built-in operators that read and write $_ and @_ by default, but your own subroutines will only do that if you write code to make it happen.