Question

I have a perl script (simplified) like so:

my $dh = Stats::Datahandler->new(); ### homebrew module

my %url_map = (
    '/(article|blog)/' => \$dh->articleDataHandler,
    '/video/' => \$dh->nullDataHandler,
); 

Essentially, I’m going to loop through %url_map, and if the current URL matches a key, I want to call the function pointed to by the value of that key:

foreach my $key (keys %url_map) {
    if ($url =~ m{$key}) {
        $url_map{$key}($url, $visits, $idsite);
        $mapped = 1;
        last;
    }
}

But I’m getting the message:

Can't use string ("/article/") as a subroutine ref while "strict refs" in use at ./test.pl line 236.

Line 236 happens to be the line $url_map{$key}($url, $visits, $idsite);.

I’ve done similar things in the past, but I’m usually doing it without parameters to the function, and without using a module.

Answer 1

Since this is being answered here despite being a dup, I may as well post the right answer:

What you need to do is store a code reference as the values in your hash. To get a code reference to a method, you can use the UNIVERSAL::can method of all objects. However, this is not enough as the method needs to be passed an invocant. So it is clearest to skip ->can and just write it this way:

my %url_map = (
    '/(article|blog)/' => sub {$dh->articleDataHandler(@_)},
    '/video/'          => sub {$dh->nullDataHandler(@_)},
); 

This technique will store code references in the hash that when called with arguments, will in turn call the appropriate methods with those arguments.

This answer omits an important consideration, and that is making sure that caller works correctly in the methods. If you need this, please see the question I linked to above:

How to take code reference to constructor?