How to verify the name of a file?

I have a function that returns a file for the user avatar and I want to create tests for it. What I want to do is to check the name of the file.

This is the function:

sub get_avatar {
   my $self = shift;
   my $username = $self->stash('username');

   my $home = Mojo::Home->new;
   $home->detect('Project');
   my $path = $home->child('users', 'avatars', "$username");

   $path = $home->child('img', 'default.png') if !(-e $path);

   $self->render_file('filepath' => $path);
}

And this is the test:

$file = $t->get_ok('/user/username/avatar')->status_is(200);
  //use Data::Dumper;
  //diag Dumper($file);

ok $file =~ 'username';

I want to check if the name of the $file is equivalent to 'username'(which is the name of the file from the server) or 'default' if it is a default avatar.