Front page | perl.perl5.porters |
Postings from August 2008
On Mon, Aug 18, 2008 at 09:00:06AM -0700, Ed Avis wrote:
> # New Ticket Created by "Ed Avis"
> # Please include the string: [perl #58072]
> # in the subject line of all future correspondence about this issue.
> # <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=58072 >
>
>
> This is a bug report for perl from eda@waniasset.com,
> generated with the help of perlbug 1.36 running under perl 5.10.0.
>
>
> -----------------------------------------------------------------
> [Please enter your report here]
>
> When a regexp has capturing parentheses it sets match variables from
> $1 upwards. This can sometimes cause trouble, for example
>
> <http://rt.cpan.org/Ticket/Display.html?id=36956>
> <http://rt.perl.org/rt3/Public/Bug/Display.html?id=23140>
> <http://rt.perl.org/rt3/Public/Bug/Display.html?id=22369>
>
> In most situations you can avoid the problem by following two rules:
> do not pass $1 as an argument to subroutines, and any subroutine
> should unpack @_ first before doing any regexp operations. But this
> is not always possible, as in the first bug report above for NEXT.
>
> It would simplify these situations to have a flag meaning do not
> change the magical match variables. Perhaps it could be called /l but
> the exact letter is not important at all. Then
>
> my $str = 'hello';
> my ($x, $y) = ($str =~ /(\w)(\w)/l);
>
> would set $x to 'h' and $y to 'e' as now, but would not touch the old
> values of $1 and $2.
>
> In module code where you have to be cautious about trampling on other
> people's $1 and $2, the /l flag would let you use regular expressions
> without a lot of shenanigans.
You can already do this easily currently:
"foo" =~ /(\w)(\w)/;
say "$1 $2";
my $str = 'hello';
my ($x, $y) = do {$str =~ /(\w)(\w)/};
say "$x $y $1 $2";
__END__
f o
h e f o
Abigail
Thread Previous