Closer examination revealed that the value of @_ varies depending on how the function is called. 
#!/usr/bin/perl -w
use strict;
use Hook::LexWrap;
use Data::Dumper;

sub get { return "Foo!" }
wrap get, post => sub { print Dumper(\@_) };
my @n = get();
my $n = get();
get();

[download]
And the output -
$VAR1 = [
          [
            'Foo!'
          ]
        ];
$VAR1 = [
          'Foo!'
        ];
$VAR1 = [
          bless( sub { "DUMMY" }, 'Hook::LexWrap::Cleanup' )
        ];

[download]
Looking at the documentation, the author states that:
In a post-wrapper, $_[-1] contains the return value
produced by the wrapped subroutine. In a scalar return
context, this value is the scalar return value. In an
list return context, this value is a reference to the
array of return values. $_[-1] may be assigned to in a
post-wrapper, and this changes the return value accordingly.

[download]
 What the author didn't mention is that in a void context, $_[-1] is the object. Thus giving you the error in 'warn'.

In reply to Re: Hook::LexWrap doesn't capture return value of subroutine in post() wrapper by Roger
in thread Hook::LexWrap doesn't capture return value of subroutine in post() wrapper by meonkeys

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