use strict;
use warnings;

my $data_set_name;
my $another_data_set;

open my $data2, '<',  \$data_set_name or die "some message $!";
print  $_ while (<$data2>);
print "\n";

open my $data3, '<',  \$another_data_set or die "some message $!";
print $_ while (<$data3>);
print "\n";

print "NOW READING MYSELF...\n";
seek(DATA,0,0);
print $_ while (<DATA>);

# Using BEGIN blocks allows potentially lengthy data
# to appear at the end of the program file

BEGIN{
$data_set_name = <<END;
asdf
qerg
5666
END
}

BEGIN{
$another_data_set = <<EOF
46464
9187
jjh
EOF
}

__DATA__