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Re: Declaring a Variable [for BEGINNERS]

by scooper (Novice)
on Dec 28, 2006 at 04:26 UTC ( #591978=note: print w/ replies, xml ) Need Help??


in reply to Declaring a Variable [for BEGINNERS]

Always put the for loop iterator variables as 'my' inside the for loop.

foreach my $region (@regions) { # something happening in the loop }
If you write
my $region foreach $region (@regions) { # something happening in the loop }
Perl silently declares a new lexical variable (also named $region) as the iterator variable. The new $region is scoped to the loop block and hides any variable $region from the outer scope. By explicitly putting the my in the foreach, you're reminding yourself of this behaviour. You're avoiding the misconception that the last value of $region will be available after the for loop (it won't, however you try to scope it). If you want that information you have to save it to an outside variable inside the loop
my $latest_region; foreach my $region (@regions) { $latest_region = $region; # something happening in the loop last if (some condition); } print "last region considered was $latest_region\n";
Most of this information lifted from "Non-Lexical Loop Iterators", 'Always declare a for loop iterator variable with my', in "Perl Best Practices", by Damian Conway


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