strange subs

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

while searching for perl codes in the internet I found something pretty strange(to me), I don't remember what site it was(in the time I didn't got a chance to copy the url sorry) but the code was like this:

sub foo ($$)
{
   #somecode
}
[download]

what are those $$ in the sub name for ? I didn't found any doc about it (don't know what to search for) can someone point me to some ?

Comment on strange subs Download Code

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Re: strange subs by si_lence (Deacon) on Jun 10, 2009 at 12:10 UTC
It is called a prototype. It lets you put constraints on the number and types of arguments. cheers si_lence	[reply]
Re: strange subs by dHarry (Abbot) on Jun 10, 2009 at 12:08 UTC
perlsub	[reply]
Re: strange subs by shmem (Chancellor) on Jun 10, 2009 at 13:17 UTC
As others said, those `$$` are prototypes. See perlsub. Don't use them unless you know what you do - see FMTYEWTK about prototypes.	[reply] [d/l]
Re: strange subs by Unforgiven (Hermit) on Jun 10, 2009 at 14:25 UTC
Others already mentioned reading perlsub, which looks to cover the topic well, but I thought I'd mention that there's also a good sized section on this in "Programming Perl" as well. From the looks of it though, you'd be fine just reading one or the other.	[reply]
Re: strange subs by Anonymous Monk on Jun 10, 2009 at 12:26 UTC
thanks to both of you. I founded.	[reply]
Re^2: strange subs by rovf (Priest) on Jun 10, 2009 at 12:54 UTC
Make sure that you also read Gratuitous use of Perl Prototypes. -- Ronald Fischer <ynnor@mm.st>	[reply] [d/l]
Re^2: strange subs by perlsaran (Sexton) on Jun 11, 2009 at 04:01 UTC
sub foo($$) # it strictly allows two scalar values as a arguments from the function call or else it throw error..In normal case it dont it accepts as many number of arguments Thanks everyone for suggesting perlsub and other usefull links	[reply]
Re: strange subs by Anonymous Monk on Jun 11, 2009 at 11:22 UTC
This is funciton protyping, indicating that this funciton can take will expect two scalars as an argument	[reply]
Re: strange subs by paradox242 (Initiate) on Jun 11, 2009 at 23:20 UTC
That's a subroutine prototype. The '$$' indicates that it accepts exactly two arguments, both of which will be evaluated in a scalar context. See perldoc perlsub.	[reply]
Re: strange subs by Anonymous Monk on Jun 11, 2009 at 23:24 UTC
You're referring to what we call prototy-- oh, nevermind.	[reply]
Re: strange subs by Anonymous Monk on Jun 15, 2009 at 09:11 UTC
sub foo($$) it mean you need to give two scalar for subroutine. ex: foo( $name, $val);	[reply]