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FAQ 7.20 Why doesn't "my($foo) = <FILE>;" work right?

 
 
PerlFAQ Server
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      02-28-2011
This is an excerpt from the latest version perlfaq7.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

7.20: Why doesn't "my($foo) = <FILE>;" work right?

"my()" and "local()" give list context to the right hand side of "=".
The <FH> read operation, like so many of Perl's functions and operators,
can tell which context it was called in and behaves appropriately. In
general, the scalar() function can help. This function does nothing to
the data itself (contrary to popular myth) but rather tells its argument
to behave in whatever its scalar fashion is. If that function doesn't
have a defined scalar behavior, this of course doesn't help you (such as
with sort()).

To enforce scalar context in this particular case, however, you need
merely omit the parentheses:

local($foo) = <FILE>; # WRONG
local($foo) = scalar(<FILE>); # ok
local $foo = <FILE>; # right

You should probably be using lexical variables anyway, although the
issue is the same here:

my($foo) = <FILE>; # WRONG
my $foo = <FILE>; # right



--------------------------------------------------------------------

The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
 
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