Greg Sabino Mullane wrote:

Tom Lane asked:

Please, tell me that isn't so.  $a is a reserved name now?  What was
Larry thinking?
It's not that bad, really. $a and $b have special meaning inside of
a sort subroutine as the two items being compared. Thus, you can write
something like this:

my @crooks = sort { lc $a cmp lc $b } @whitehouse;

 to create a list sorted by lowercase (albeit not in the most efficient
matter). This will work even with "use strict" turned on, as $a and $b
will not trip Perl's strict-mode checking of undeclared variables. So,
the danger is very minor, but it's a good practice to not use them for
temporary variables in a script.

I recently lost quite some time tracking down a piece of spurious data persistence that eventually turned out to be due to use of an undeclared $a that strict mode failed to detect, so it's not so minor, really.

In retrospect, the choice of names for sort comparison operands was poor, as I suspect Larry would agree, but it's been there ever since I have been using perl (around 12 years now, iirc).



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