Distributing the data for a single student across multiple arrays is asking for trouble. Much better to keep each student’s data in the same structure. So I would reverse the architecture: instead of a hash of arrays, use an array of hashes. Or, more precisely, an array of blessed hashes (objects). Something like this:

#! perl
use strict;
use warnings;

{
    package Student;

    sub new
    {
        my ($class,   $name,      $age,
            $regd_no, $phone_num, $mark, $pass_year) = @_;
        my  $self = {
                        NAME    => $name,    AGE       => $age,
                        REGD_NO => $regd_no, PHONE_NUM => $phone_num,
                        MARK    => $mark,    PASS_YEAR => $pass_year
                    };

        return bless $self, $class;
    }

    sub display
    {
        my ($self) = @_;

        if ($self)
        {
            print 'Name:       ', $self->{NAME},      "\n";
            print 'Age:        ', $self->{AGE},       "\n";
            print 'Regd no:    ', $self->{REGD_NO},   "\n";
            print 'Phone num:  ', $self->{PHONE_NUM}, "\n";
            print 'Mark:       ', $self->{MARK},      "\n";
            print 'Pass year:  ', $self->{PASS_YEAR}, "\n";
        }
    }
}

my @students;

while (<DATA>)
{
    chomp;
    push @students, Student->new(split /:/);
}

find_student('x3')->display();

sub find_student
{
    my ($regd_no) = @_;

    for (@students)
    {
        return $_ if $_->{REGD_NO} eq $regd_no;
    }

    return undef;
}

__DATA__
A:20:x1:phone4:72:2011
B:19:x2:phone2:55:2012
C:22:x3:phone3:83:2009
D:23:x4:phone1:69:2008
[download]

Output:

17:18 >perl 578_SoPW.pl
Name:       C
Age:        22
Regd no:    x3
Phone num:  phone3
Mark:       83
Pass year:  2009

17:22 >
[download]

Hope that helps,