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Postings from October 2003
On 9 Oct 2003, at 19:38, Jonathan Eisler (via RT) wrote:
> I think this is a bug, but it may just be strange behaviour: global
> matching (ie: m/.../g ) behaves differently when the extracted results
> are
> saved to lexical variables or when the $1, $2, etc, implicit variables
> are
> used.
>
> Consider:
>
> my $text = "Foo\nBar\n";
> while ( $text =~ /(\w+)/g ) { print $1, "\n" }
>
> The above script prints 2 lines to standard out, as expected:
> "Foo\nBar\n".
Yes, thats because in a scalar context m//g will remember where it left
off and the next match will start where the previous left off.
> Now consider:
>
> my $text = "Foo\nBar\n";
> while ( my ( $name ) = ( $text =~ /(\w+)/g ) ) { print $name, "\n" }
>
> The above script goes into an infinite loop, printing "Foo\n" to stdout
> over and over.
Correct. the () puts the m//g into a list context. In a list context
m//g will return all matches as a list. As you only have one variable
in the my() you only see the first match. Each time m//g is called in a
list context it restarts from the start of the string.
> Shouldn't the two scripts behave equivalently?
No.
Graham.
>
> Note, I've tested this on:
> perl 5.00503 for freebsd
> perl 5.8.1 for linux
> perl 5.8.0 for darwin
> I get the same behaviour on all 3.
>
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