use warnings; 
use strict;
sub myfunc(@) {
    my $default_subfunc =  sub {
        local $"=',';
        return "my default code block: (@_)\n";
    };
    my $subfunc = ( 'CODE' eq ref $_[0] ) ? shift : $default_subfunc;
    return $subfunc->(@_);
}

#3: no CODEREF
print myfunc 1, 2, 3;

#2a: two-line version, with comma:
my $alternate = sub { "alt: sizeof LIST = " . scalar(@_) . "\n" };
print myfunc $alternate, 1..10;

#2b: one-line version, with comma:
print myfunc sub { local $"=';'; return "oneliner: @_\n" }, qw/hello world/;

#2fail: one-line version, no comma, no sub:
eval qq|  # this eval-wrapper prevents the compiler from crashing, so the previous examples will still run
print myfunc { local $"=';'; return "oneliner: @_\n" } qw/hello world/;
|;
if($@) {
    my $x = $@;
    $x =~ s/^/\t/gm;
    print "ERROR:{\n$x\n}\n";
}

# I assume you already knew the & prototype, to mimic _just_ #2's syntax
sub otherfunc(&@) {
    my $subfunc = shift;
    return $subfunc->(@_);
}

print otherfunc { "otherfunc always needs a coderef: @_\n" } 5..7;
print otherfunc sub { $alternate->(@_) }, 2,3,5,7,11;

print "END\n";