Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!munnari.oz.au!yarra-glen.aaii.oz.au!pem
From: pem@yarra-glen.aaii.oz.au (Paul E. Maisano)
Newsgroups: comp.lang.perl
Subject: when is pass by reference necessary?
Message-ID: <1991Mar28.053132.7061@yarra-glen.aaii.oz.au>
Date: 28 Mar 91 05:31:32 GMT
Organization: Australian Artificial Intelligence Institute
Lines: 30

Consider this program:
(don't run it unless you need a file called file.dat in the current dir.)

#!/usr/bin/perl

($debug = 1, shift) if $ARGV[0] eq '-d';

sub my_open {   # called with (file_handle, name) 
    local(*F, $name) = @_;
    if ($debug) {
	open(F, ">&STDOUT") || die "can't dup STDOUT: $!\n";
    }   
    else {
	open(F, ">$name") || die "open $name: $!\n";
    }   
}

# should this be: &my_open(*X, "file.dat");
&my_open(X, "file.dat");
print X "hello world\n";
close(X);


When I wrote this, I intended to pass the file handle as *X but I forgot
the *. It still worked so I wondered if I was confused about why I thought
the * was necessary. Is it necessary ? 

---
Paul Maisano,
Australian Artificial Intelligence Institute