It works with a sub ref returned from can for me:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package My::Url;

    sub new {
        my $class = shift;
        bless {@_}, $class
    }

    sub url {
        my ($self, $node_id) = @_;
        $self->{url} . '?node_id=' .  $node_id
    }
}

my $o = 'My::Url'->new(url => 'http://www.perlmonks.org/');
my $methodname = 'url';
my $methodref = $o->can($methodname);
say $o->$methodref(1142751);
[download]

But even if it didn't, you know the name, right? You used it as the argument to can.

Update: It's documented.