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10. I/O > Indirect Filehandles

Indirect Filehandles

Use indirect filehandles.

Indirect filehandles provide a much cleaner and less error-prone alternative to bareword filehandles, and from Perl 5.6 onwards they're as easy to use as barewords. Whenever you call open with an undefined scalar variable as its first argument, open creates an anonymous filehandle (i.e., one that isn't stored in any symbol table), opens it, and puts a reference to it in the scalar variable you passed.

So you can open a file and store the resulting filehandle in a lexical variable, all in one statement, like so:

open my $FILE, '<', $filename
    or croak "Can't open '$filename': $OS_ERROR";

The my $FILE embedded in the open statement first declares a new lexical variable in the current scope. That variable is created in an undefined state, so the open fills it with a reference to the filehandle it's just created, as described earlier.


  

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