Why do I need a slash before my -- \my -- in getopts

tphyahoo has asked for the wisdom of the Perl Monks concerning the following question:

I stumbled across this feature of getopts in

Basically @ARGV > 0 and getopts('a:', \my %opt) or die << "USAGE";

works, but "my" instead of "\my" doesn't work. And fwiw, neigher does {my %opt}.

What's up with that? What is that backslash doing? And is there some less arcane way to parse args, with Getopts::Std or one of the other arg handling modules?

Thanks!

Edited by planetscape - linkified link

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Re: Why do I need a slash before my -- \my -- in getopts by Fletch (Bishop) on Apr 12, 2006 at 13:31 UTC
The backslash is taking a reference to `%opt` (so `getopts` recieves a hashref which it populates). It's no different than `my %opt; @ARGV > 0 and getopts( 'a:', \%opt ) or die <<"USAGE";` [download] or `my $opt = {}; @ARGV > 0 and getopts( 'a:', $opt ) or die <<"USAGE";` [download] Just looks a little funy. And I usually use Getopt::Long, but that's just me (actually recently I use this more often, but that's not really going to help you . . . :).	[reply] [d/l] [select]
Re: Why do I need a slash before my -- \my -- in getopts by ikegami (Patriarch) on Apr 12, 2006 at 16:23 UTC
First, a primer `{ ... }` creates a new (anonymous) hash. The hash is initialized using the specified list. A reference to the new hash is returned. `\%hash` simply returns a reference to the specified hash. Now, in context `{ my %opts }` first creates hash `%opts`. Then it creates a new (anonymous) hash. The anonymous hash is initialized with the contents of `%opts` (which is empty). A reference to the anonymous hash is returned (and passed to `getopts`). That doesn't work because `getopts` populates the anonymous hash, which is freed as soon as `getopts` returns because you never saved a reference to it. And `%opts` is left untouched because `getopts` doesn't know it exists. When you use `\%opts`, on the other hand, you pass a reference to `%opts`, so `getopts` populates `%opts` Fletch covered the role of `my` in his post.	[reply] [d/l] [select]

First, a primer

Now, in context