The values of $status, $soc, and $subscriber are based on @row_text, but that array is never populated. Each of those scalars will be undef.

For other interested monks, here's my feeble attempt at reformatting:

use warnings;
use strict;

&readfile;

sub readfile{ 
    my $input_FL;
    my @file_row;
    my @row_text;
    my $row_data;
    my $row_text;
    my $line =0; 
    my $status;
    my $soc;
    my $subscriber;
    my @ar_OR_STA;
    my @ar_OR_SOC;
    my @ar_OR_SUB; 
    $input_FL = "C:\\taj.txt"; 
    chomp $input_FL; 
    #remove enter key or any spaces 
    open(IN_FL, $input_FL) || die ("unable to open directory"); 
    while (<IN_FL>){ 
        @file_row=<IN_FL>; 
        print $#file_row; 
    }#while 
    close IN_FL; 
    foreach(@file_row) { 
        while ($line < $#file_row +1){ 
            $row_data =$file_row[$line];
            chop ($row_data); 
            next unless /\S/; # only use lines that contain +something
+ else than spaces 
            #print "$row_data\n"; 
            if ($row_data =~ /^[d]/) { 
                $status = $row_text[0]; 
                $status =~ s/(\W+)/ /gs; #Eliminate all non-+word char
+acters followed by space. 
                #$ar_OR_STA[$i]=$status; #Here $[=1, so @ar_STA[0] doe
+s not have any value. Original Array of Status 
                push (@ar_OR_STA,$status); 
                print "@ar_OR_STA\n"; 
                $soc = $row_text[1]; 
                $soc =~ s/(\W+)/ /; #Eliminate all non-word characters
+ followed by space. 
                #$ar_OR_SOC[$i-1]=$soc; #Here $[=1, so @ar_STA[0] does
+ not have any value. Original Array of Status 
                $subscriber = $row_text[3]; 
                $subscriber =~ s/(\D+)/ /; #Eliminate all non-digits f
+ollowed by space. 
                #$ar_OR_SUB[$i-1]=$subscriber; #Here $=1, so @ar_SUB[0
+] does not have any value.Original Array of Subscriber
            }
            else { 
                print " File is invalid\n";
            }
            $line++;
        }#while
    }#foeach
}
# Here, I get Uninitaialized value in substitution(s///) in the follow
+ing lines?Anybody Know why?
$status =~ s/(\W+)/ /gs;
$soc =~ s/(\W+)/ /;
$subscriber =~ s/(\D+)/ /; # and use of initialized value in join or s
+tring at print "@ar_OR_STA\n";
[download]

As an aside, I think changing the value of $[ could have some very confusing unwanted consequences later in this code's life. (I quote perlvar: "Its use is highly discouraged.") If you must go through with that, use local to limit the scope (although I can't tell that you haven't from the code you posted).

Perl is crazy. if you put a space after the "=", you will get this error. Something like this: $s = ~s/abc/def/g; This is ridiculas.

That's not "putting a space after the =", that's breaking the =~ operator by spelling it wrong. Crazy? What's crazy is thinking that putting spaces in the middle of operators should have no effect. Thinking = ~ should work is as crazy as thinking that e q should work, or s ub, or m y.

I suggest that you have a look at Writeup Formatting Tips which tells you how to format your questions. The bottom of the preview page has a quick guide to available tags and some handy links.

You will get a better response if your questions are well presented. At a minimum use <p> </p> pairs for paragraphs and <code> </code> for literal code or data blocks.

Once you have reformatted your question I will have a look at it;-)

Well done kyle! I should have realised that [ and ] were being interpreted as link metacharacters.

There are a number of odd things about this script. I'll start with a couple of minor points, The code and comments in these lines are contradictory

$status =~ s/(\W+)/ /gs; #Eliminate all non-word characters followed b
+y space.
[download]

$soc =~ s/(\W+)/ /; #Eliminate all non-word characters followed by spa
+ce.
[download]

$subscriber =~ s/(\D+)/ /; #Eliminate all non-digits followed by space
+.
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The more egregious error is the logic is badly flawed. This nested loop

foreach (@file_row) {
    while ( $line < $#file_row + 1 ) {
        $row_data = $file_row[$line];
        # Processing goes here.
        $line++;
    }    #while
}    #foreach
[download]

foreach $row_data ( @file_row ) {
    # Processing goes here.
}
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while ( $row_data = <IN_FL> ) {
    # Processing here
}
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Update: I'd also change

open(IN_FL, $input_FL) || die ("unable to open directory");
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open IN_FL, $input_FL or die "unable to open $input_FL:$!";
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use Data::Dumper;

...


print Dumper(\@array); # OR
print Dumper(\%hash);
[download]

I had the same problem and just fixed it! The problem is the initial assignment of the variables.

e.g.

my $status = $myhash{'key1'};
$status =~ s/\t/    /g;
[download]

will give an error IF the value of $myhash{'key1'} is not defined.

This was my fix:

my $status = $myhash{'key1'} || '';
$status =~ s/\t/    /g;
[download]

no more error!