Question

I am doing pass-by-reference like this:

use strict;
use warnings;

sub repl {
    local *line = \$_[0]; our $line;
    $line = "new value";
}

sub doRepl {
    my ($replFunc) = @_;
    my $foo = "old value";
    $replFunc->($foo);
    print $foo; # prints "new value";
}

doRepl(\&repl);

Is there a cleaner way of doing it?

Prototypes don’t work because I’m using a function reference (trust me that there’s a good reason for using a function reference).

I also don’t want to use $_[0] everywhere in repl because it’s ugly.

Answer 1

Have you looked at Data::Alias? It lets you create lexically-scoped aliases with a clean syntax.

You can use it to create pass-by-reference semantics like this:

use strict;
use warnings;

use Data::Alias;

sub foo {
    alias my ($arg) = @_;
    $arg++;
}

my $count = 0;

foo($count);

print "$count\n";

The output is 1, indicating that the call to foo modified its argument.