@_ is easy(tm)

jay.pl

use 5.26.0;
package Foo;

sub new { bless {} }

sub bar {
  my $baz = sub {
    return join " ", @_;
  };
  say "Current code:  " . $baz->();
  say "Proposed code: " . $baz->(@_);
}


package main;

my $foo = Foo->new;
$foo->bar(3,4,5);

sweth.pl

package Foo;
use Modern::Perl;
use DDP;
sub new {
    say '@_ is ', np( @_ );
    my $class = shift;
    my $self = { @_ };
    bless( $self, $class );
    say "Instantiating $class as ", np( $self );
    return( $self );
}
sub say_hello {
    say "Hello";
}
sub generate_coderef {
    say '@_ entering ', (caller(0))[3], ' is ', np( @_ );
    my $self = shift;
    say '@_ in ', (caller(0))[3], ' after shift is ', np( @_ );
    my $coderef = sub {
        say '@_ entering $coderef ', (caller(0))[3], ' is ', np( @_ );
        $self->say_hello;
    }
}
my $foo = new Foo(1=>2, 3=>4);
my $coderef = $foo->generate_coderef(11,22,33);
$coderef->();
$coderef->(44,55,66);
1;