Please find the code below, which meets your requirement.

#!/perl/bin/perl 

use strict;
use warnings;

use Data::Dumper;

my $fname = "Designations.txt";
open (WXYZ, $fname) or die "Couldn't open file Designations.txt, $!";

while(1) # This loop is to continously get the user input.
{
        print "Enter First Name or Last Name: \n \n";
        my $user_input = <STDIN>;
        chomp($user_input);

        if(defined $user_input and length $user_input)
        {
                print "Entered name is : $user_input \n";
                &find_details($user_input);
                seek(WXYZ,0,0);
        }
}

sub find_details{

        my ($uinput) = @_;

        my @array;

        while (<WXYZ>) {
                chomp;
                next if(/\-+/ || /SLNO/);

                @array = split /\s+/,$_;
                my $input;
                foreach $input (@array[1,2]){
                        print ">>$input<<\n";
 if ($input =~ /$uinput/)
                        {
                                print "$input,$array[3]\n";
                                return;
                        }
                }
        }
        print ">>>>>>>>>>>>>>>>>>>>>>>>>>>Sorry! User Details not avai
+lable<<<<<<<<<<<<<<<<<<<<<<<<<<\n" ;
}
close(WXYZ);
[download]

1. The first while loop continues runs to get the userinut and calls a find_details function if user enters valid input.

2. find_detils function reads each line and splits based on space character and saves into array, a foreach inside the function searchs your input against firstname and lastname. If user input matchs, its print the username and designation.

3.After the function return, I do seek to move the file pointer to move to the begging of the file to make the file ready to search the next input.