Purpose of $$ in subroutine

Hi everybody,

I was reading perlfaq7.pod, 7.15: How can I pass/return a {Function,  
FileHandle, Array, Hash, Method, Regex}?

In one of the examples it shows how regular expressions can be passed to  
subroutines:

                 sub compare($$) {

                    my ($val1, $regex) = @_;
                    my $retval = $val1 =~ /$regex/;
                    return $retval;

                 }

                 $match = compare("old McDonald", qr/d.*D/i);

I know the special variable $$ contains the process number of the Perl  
running this script, but just wanted to know its purpose in compare($$).

Many thanks,

Dave

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• Purpose of $$ in subroutine by Dave Tang
• Re: Purpose of $$ in subroutine by Chas. Owens
• Re: Purpose of $$ in subroutine by Dave Tang
• Re: Purpose of $$ in subroutine by Chas. Owens
• Re: Purpose of $$ in subroutine by Dermot
• Re: Purpose of $$ in subroutine by Chas. Owens
• Re: Purpose of $$ in subroutine by John W. Krahn