Why am I getting a syntax error when I pass a coderef to this prototyped Perl subroutine?

Question

This is the code:

sub function($&) {
    my $param1 = shift;
    my $code = shift;
    # do something with $param1 and $code
}

If I try to call it like this:

function("whatever") {
    print "i'm inside the coderef\n";
}

I get Not enough arguments for MyPackage::function at x.pl line 5, near ""whatever" { ". How can I call it without having to add sub in front of the code block?

Answer 1

Put the coderef argument first:

sub function (&$) {
    my $code = shift;
    my $param1 = shift;
    # do something with $param1 and $code
}

function { print "i'm inside the coderef\n" } "whatever";

See the perlsub man page, which reads in part:

An "&" requires an anonymous subroutine, which, if passed as the first argument, does not require the "sub" keyword or a subsequent comma.