use strict;
use warnings;

{
    package Foo;
    use Devel::Caller qw(called_as_method);
    use Carp;
    
    sub new { bless {}, shift };
    

    sub display {
        my $self;
        
        # extract $self if called as a method
        $self = shift if called_as_method(0);

        # check we have even number of key/value pairs
        croak "missing key/value (@_)" unless @_ % 2 == 0;

        # make a hash of our key/value pairs
        my %hash = @_;

        # show how we were called
        my $type = "subroutine";
        $type = (ref($self) ? "object" : "class") . " method" if $self;
        print "$type called with\n";
        while (my ($k, $v) = each %hash) { print "$k = $v\n" };
        print "\n";
    };
};

Foo->new->display(a => 400, b=>800);
Foo->display(a => 400, b=>800);
Foo::display(a => 400, b=>800); 
Foo::display(a => 400, b=>800, 900);