Hash slice problem

hash_slice.pl

#!/usr/bin/perl

use strict;
use warnings;

foreach my $var (qw(REQUEST_METHOD PATH_INFO CONTENT_LENGTH CONTENT_TYPE)) {
    $ENV{$var} = $var;
}

# my ($req_method,$path_info,$content_length,$content_type)
#      = @{ %ENV }{qw|REQUEST_METHOD PATH_INFO CONTENT_LENGTH
#               CONTENT_TYPE|};
my ($req_method,$path_info,$content_length,$content_type)
     = @ENV{qw|REQUEST_METHOD PATH_INFO CONTENT_LENGTH CONTENT_TYPE|};

print "req_method     = $req_method\n";
print "path_info      = $path_info\n";
print "content_length = $content_length\n";
print "content_type   = $content_type\n";

hash_slice_bad.pl

#!/usr/bin/perl

use strict;
use warnings;

foreach my $var (qw(REQUEST_METHOD PATH_INFO CONTENT_LENGTH CONTENT_TYPE)) {
    $ENV{$var} = $var;
}

my ($req_method,$path_info,$content_length,$content_type)
     = @{ %ENV }{qw|REQUEST_METHOD PATH_INFO CONTENT_LENGTH
              CONTENT_TYPE|};

print "req_method     = $req_method\n";
print "path_info      = $path_info\n";
print "content_length = $content_length\n";
print "content_type   = $content_type\n";

# Can't use string ("61/128") as a HASH ref while "strict refs" in use at ./foo.pl line 11.

output.txt

$ /usr/local/apps/perl-5.12.4/bin/perl --version | sed -n 2p
This is perl 5, version 12, subversion 4 (v5.12.4) built for i686-linux
$ /usr/local/apps/perl-5.12.4/bin/perl hash_slice.pl
req_method     = REQUEST_METHOD
path_info      = PATH_INFO
content_length = CONTENT_LENGTH
content_type   = CONTENT_TYPE
$ /usr/local/apps/perl-5.12.4/bin/perl hash_slice_bad.pl 
Can't use string ("61/128") as a HASH ref while "strict refs" in use at hash_slice_bad.pl line 11.