Re^2: What's the opposite of // (err) operator?

Nice. I always forget about the low-precidence variations. Combining that with GrandFather's reply gives:

my $x= blahblah...  err return;
... continue using $x
[download]

That reads with the proper "flow" and connotations: if I find an undef after this computation, quit now.

Now what version of Perl introduced err?

later... Apparently not the one I'm using! The construct above gives an error, "missing operator before err?", but the syntax works with or so it's not the precedence, but rather it seems not to know what err means!

The perldoc perlop (I'm reading for Perl 5.10.1 since that's what I'm using) has a section called “Logical or, Defined or, and Exclusive Or”, and it discusses the low-precedence or and xor but doesn't actually mention any kind of "defined or" keyword. How odd.

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Re^3: What's the opposite of // (err) operator? by Tux (Canon) on May 11, 2011 at 06:55 UTC
Do not use the `err` keyword. It was introduced in the 5.9.x development series, and made available to all the 5.8.x builds by patches (maintained by me). The community however decided that `err` did not have enough good reasons to stay and was removed later on. That made me feel sad, but I am not the one that makes the final decision. The bottom line is that `err`, which was a special type of operator that could be overruled by a local function with the same name, is not available in 98% perl. Do not use it. Enjoy, Have FUN! H.Merijn	[reply] [d/l] [select]
Re^4: What's the opposite of // (err) operator? by John M. Dlugosz (Monsignor) on May 11, 2011 at 07:11 UTC
Because it conflicted with functions people had named? That's always the problem with adding a keyword. The docs still show some vestiges. That ought to be fixed.	[reply]
Re^5: What's the opposite of // (err) operator? by eyepopslikeamosquito (Archbishop) on May 11, 2011 at 07:49 UTC
Because it conflicted with functions people had named? AFAICT, it was mainly a "religious" argument. There were some very long P5P threads arguing about the merits of the name "err" versus "dor" (I personally like "err"). Larry changed it to "orelse" for Perl 6 last time I looked. For more detail and links see: Re^3: RFC: Defined-Or for before Perl 5.10 and What happened to dor and err in Perl 5.10?.	[reply]
Re^3: What's the opposite of // (err) operator? by ikegami (Patriarch) on May 11, 2011 at 06:55 UTC
There isn't one. But then again, you don't need one. A low-precedence variation would cause a needless assignment to be performed. `my $x = EXPR // return; ... continue using $x` [download]	[reply] [d/l]
Re^4: What's the opposite of // (err) operator? by John M. Dlugosz (Monsignor) on May 11, 2011 at 07:14 UTC
Very interesting. So the precedence of // is low enough so it uses everything except the assignment as the left arg. It seems odd to me to return in the middle of a value-bearing expression, but I'm too used to C++. Thanks for pointing that out.	[reply]
Re^5: What's the opposite of // (err) operator? by Tux (Canon) on May 11, 2011 at 07:17 UTC
What version of perl, and which part of the docs? I can "fix" it for the development branch. Enjoy, Have FUN! H.Merijn	[reply]
Re^6: What's the opposite of // (err) operator? by John M. Dlugosz (Monsignor) on May 11, 2011 at 07:30 UTC
Re^7: What's the opposite of // (err) operator? by Tux (Canon) on May 11, 2011 at 09:41 UTC
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Re^5: What's the opposite of // (err) operator? by ikegami (Patriarch) on May 11, 2011 at 15:28 UTC
Well, it depends on the expression. You can always use parens around the expressions. They should rarely be required, though, since the expression is probably an array or hash lookup, or a function call. (I use parens on around function call argument lists.)	[reply]