No, you're quite right. I was being stupid and messed up, will correct that in a second so as not to confuse others.

The precedence issue is moderately easy to explain in this context. There's a standard Perl idiom

This is the equivilent to

as the 'or' is evaluated after the open command.

If you were to try

you may be surprised to know you'll never get the error message, this is because the || operator is evaluated before the open and so this is actually equivilent to

and so would only die if the string literal "file.txt" was blank. Not good. You get a similar thing with thing happening quite often.

Moral of this story: Generally use || for defaulting values ($a = $b || $c), but use 'or' for logic control similar to the above.

Oh yeah, and make sure your code dies when it gets an error, not when it doesn't.. I seem to have failed on this one