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I usually loop through lines in a file using the following code: open my $fh, '<', $file or die "Could not open file $file for reading: $!\n"; while ( my $line = <$fh> ) { ... } However, in answering another question , Evan Carroll edited my answer, changing my while statement to: while ( defined( my $line = <$fh> ) ) { ... } His rationale was that if you have a line that's 0 (it'd have to be the last line, else it would have a carriage return) then your while would exit prematurely if you used my statement ( $line would be set to "0" , and the return value from the assignment would thus also be "0" which gets evaluated to false). If you check for defined-ness, then you don't run into this problem. It makes perfect sense. So I tried it. I created a textfile whose last line is 0 with no carriage return on it. I ran it through my loop and the loop did not exit prematurely. I then thought, "Aha, maybe the value isn't actually 0 , maybe there's something else there that's screwing things up!" So I used Dump() from Devel::Peek and this is what it gave me: SV = PV(0x635088) at 0x92f0e8 REFCNT = 1 FLAGS = (PADMY,POK,pPOK) PV = 0X962600 "0"\0 CUR = 1 LEN = 80 That seems to tell me that the value is actually the string "0" , as I get a similar result if I call Dump() on a scalar I've explicitly set to "0" (the only difference is in the LEN field -- from the file LEN is 80, whereas from the scalar LEN is 8). So what's the deal? Why doesn't my while()</code

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