There are many ways to use config files within perl, one popular way is with YAML.

appconf.yaml:

dsn: 'foo'
user: 'userid'
password: 'supersecret'
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configtest.pl:

#!/usr/bin/perl

use strict;
use warnings;
use YAML::XS 'LoadFile';

my $config = LoadFile('appconf.yaml');

my $dsn = $config->{dsn};
my $user = $config->{user};
my $password = $config->{password};

print "dsn: $dsn - user: $user - password: $password\n";
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Update: forgot the output:

dsn: foo - user: userid - password: supersecret
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• config
• Task::Kensho lists some recommended modules

Don't do it directly in Perl if you're using MySQL. Use their option file; described in DBD::mysql, and look for mysql_read_default_file. File, often named .my.cnf, looks something like (not tested, obviously)–

[client]
port=1000
host=abc01.xyz.com
user=gvenkat
password=ganesh99.
default-character-set=utf8
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Connection–

my $dbh = DBI->connect("DBI:mysql:$dbnam;mysql_read_default_file=/home
+/gvenkat/.my.cnf");
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Lock the file permissions down to 400, owned by the process user that your script uses.

This sounds very much like an XY Problem. What are you trying to accomplish through this obfuscation? It seems unlikely that you will be in an environment where perl runs with different permissions than the individual who is perusing your script. There is value in abstracting common constants that are shared across scripts, but that should probably be done with modules, e.g.

package Gvenkat5;
use strict;
use warnings;
use DBI;
require Exporter;

@EXPORT_OK = 'connect';

sub connect {
    my $port = shift || 1000;
    my $dbnam = '';
    return DBI->connect("DBI:mysql:database=$dbnam;
                         host=abc01.xyz.com;
                         port=$port",
                         'gvenkat',
                         'ganesh99')
}
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use Gvenkat5 'connect';

my $dbh = connect($ARGV[0]);
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#!user/bin/perl
use strict;
use warnings;
use Data::Dumper;

use  Config::Tiny;

my $file=<<END;
[DBname]
Port Number = 1000
host name = abc01.xyz.com
username = gvenkat
password = ganesh99
END

my $Config = Config::Tiny->new;
$Config = Config::Tiny->read( \$file );

my $portnum = $Config->{DBname}->{'Port Number'};
print "$portnum\n";
my $hostname = $Config->{DBname}->{'host name'};
print "$hostname\n";
my $username = $Config->{DBname}->{'username'};
print "$username\n";
my $password = $Config->{DBname}->{'password'};
print "$password\n";

my $href = $Config->{DBname};
print Dumper $href;

__END__
1000
abc01.xyz.com
gvenkat
ganesh99
$VAR1 = {
          'username' => 'gvenkat',
          'Port Number' => '1000',
          'host name' => 'abc01.xyz.com',
          'password' => 'ganesh99'
        };
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Update: I looked at the post from Your Mother at Re: Read from a header file like C. That seems to be the way to go for MySQL. Similar format to the above.

When updating a post place mark them. Read How do I post a question effectively?. Also you seem to have managed to post the same question 3 times now.