Auto-localization of $

repellent has asked for the wisdom of the Perl Monks concerning the following question:

I'm running v5.8.5. Will $_ be auto-localized for

    while (<>) { .. }
[download]

in the manner of

    while (local $_ = <>) { .. }
[download]

in future versions? If not, what are the impediments?

Reference: Sins of Perl Revisited

Comment on Auto-localization of $_ in while(<>) Select or Download Code

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Re: Auto-localization of $_ in while(<>) by ysth (Canon) on Feb 05, 2008 at 06:23 UTC
In perl 5.10.0, you can say `while (my $_ = <>) { }` [download] and avoid some of the problems that can happen with local when the previous $_ is aliased to something that objects to being localized. But, no, I don't see while() changing to no longer have the modified $_ available after the loop. -- Online Fortune Cookie Search	[reply] [d/l]
Re: Auto-localization of $_ in while(<>) by jwkrahn (Abbot) on Feb 05, 2008 at 06:00 UTC
It isn't localized in current versions so I don't think that it will be changed in future versions because of backward compatibility. `john@perl:~$ perl -e' my $lines = qq[one two three four ]; open F, "<", \$lines or die "open: $!"; while ( <F> ) { last if /h/; } print $_; ' three` [download]	[reply] [d/l]
Re: Auto-localization of $_ in while(<>) by kyle (Abbot) on Feb 05, 2008 at 03:55 UTC
I suppose the impediment is compatibility with older code. Code that was written with a dependency on the current (somewhat icky) behavior would break.	[reply]