Update I fixed my original proposal with a comma kluge (so that it wouldn't die when the input was a ref to an empty hash. The resulting line is so long and tortured that it hardly qualifies as a one-liner, and it is not particularly clear coding, so I don't think it is worth the trouble. FWIW, here it is (along with some minimal testing code): 

use strict;
use warnings;
use Scalar::Util 'reftype';
use Test::More 'no_plan';

sub foo {
  reftype( $_[ 0 ] ) || '' eq 'HASH' and ( my %h = %{ shift() } ), 1 o
+r die;
  return 1;
}

ok( eval { foo(+{}) }, 'empty hashref' );
ok( !eval { foo() }, 'no input' );
ok( !eval { foo( 1 ) }, 'bad input: constant' );
ok( !eval { foo( [] ) }, 'bad input: array ref' );
ok( eval { foo( +{ 1 => 1 }) }, 'good input' );
__END__

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Update #2771: Changed the code to use Scalar::Util::reftype instead of UNIVERSAL::isa, in response to chromatic's comment. If the code was tortured before, it is even more so now. The business with || '' is to silence a warning.

the lowliest monk

In reply to Re: Better way to dereference a shifted hashref arg? by tlm
in thread Better way to dereference a shifted hashref arg? by tphyahoo

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