Can someone tell me the mistake I am doing here?

Unlikely, because it isn't self-contained. You are reading 1 set of input from the INPUT_FILE handle (which I'm guessing corresponds to the sample input you have provided) and 2 other sets of input from the REPLAY_FILE handle which have not been provided to us. Without an SSCCE, the my best guess is that you don't really want a regex match at if ($rpl_sub =~ /^$line/) but rather a substring match.

See the Basic Debugging Checklist for how you can help yourself. Good luck.

you are right, I am looking for

if ($rpl_sub =~ /^$ip_var\|VALUE/)
[download]

instead of   if ($rpl_sub =~ /^$line/)

Crossposted to StackOverflow. It is considered polite to inform about crossposting, so that efforts are not duplicated.

Ok

Gordon,

For me (using your data minus the leading whitespace and with files from StackOverflow) the following:

use Data::Dumper;
use 5.01800;
use warnings;

my @cell_names;

open INPUT_FILE,"<",my $ip_file="11116963.txt"
    or die "\n!!!ERROR OPENING INPUT FILE. EXITING SCRIPT!!!\n";

while (<INPUT_FILE>) {
    #warn Data::Dumper->Dump([\$_],[qw(*_)]),' ';
    if ($_ =~ /(.*) =\n/) {
        print "\nFormat not correct on line $. of input file. Exiting 
+script\n";
        exit;
        }
    elsif ($_ =~ /(.*) =\s+\n/) {
        print "\nFormat not correct on line $. of input file. Exiting 
+script\n";
        exit;
        }
    elsif ($_ =~ /(.*) = \s+(.*)/) {
        print "\nFormat not correct on line $. of input file. Exiting 
+script\n";
        exit;
        }
    elsif ($_ =~ /^TASK_CELL_NAME\|VALUE = (.*)/) {
        my $cell_name=$1;
        unless (grep(/^$cell_name $/,@cell_names)) {
            push @cell_names,"$cell_name ";

            #$count++;
            print "\nCELL NAME: $cell_name\n";
            replace($cell_name);
            }
        } # elsif ($_ =~ /^TASK_CELL_NAME\|VALUE = (.*)/)
    } # while (<INPUT_FILE>)
close INPUT_FILE;
exit;

sub replace {

    our $rpl;
    while (<INPUT_FILE>) {
        chomp;
        #warn Data::Dumper->Dump([\$_],[qw($_)]),' ';
        my $cell=$_[0];
        if ($_ =~ /^TASK\|VALUE = (.*)/) {
            #warn Data::Dumper->Dump([\$_],[qw(*_)]),' ';
            my $task=$1;
            #chomp $task;
            $rpl=$cell.'_'.$task.'_bunch_rpl';
            print "000: $rpl\n";
            } # if ($_ =~ /^TASK\|VALUE = (.*)/)
        elsif ($_ =~ /^(.*)\|VALUE = (.*)/) {
            #warn Data::Dumper->Dump([\$_],[qw(*_)]),' ';
            my $line=$_;
            #chomp $line;
            my $ip_var=$1;
            my $ip_val=$2;
            #chomp $ip_var;
            #chomp $ip_val;
            my $look=$ip_var."|VALUE";
            open(REPLAY_FILE,"<",$rpl)
                || die "\ncannot open $rpl\n";
            while (my $rpl_sub=<REPLAY_FILE>) {
                if ($rpl_sub =~ /^$line/) {
                    print "\n 111: $ip_val";
                    }
                }
            close REPLAY_FILE;
            } # elsif ($_ =~ /^(.*)\|VALUE = (.*)/)
        elsif ($_ =~ /^\s*$/) {
            #warn Data::Dumper->Dump([\$_],[qw(*_)]),' ';
            print "\n";
            return;
            }
        } # while (<INPUT_FILE>)
    } # sub replace
[download]

yields:

CELL NAME: lfr
000: lfr_task62_bunch_rpl

 111: 2.0.9.0
 111: INLINE
 111: POWER

CELL NAME: aaa
000: aaa_task14_bunch_rpl

 111: 0.45
 111: NO
[download]

May I say that the approach of open/read/close for each name/value pair isn't very efficient.

Adding data files. '11116963.txt'

TASK_CELL_NAME|VALUE = lfr
TASK|VALUE = task62
TASK_VERSION|VALUE = 2.0.9.0
CHIP_PKG_TYPE|VALUE = INLINE
JUNK_LINE = JUNK
JUNK_LINE = JUNK
FULL_ESD|VALUE = POWER

TASK_CELL_NAME|VALUE = aaa
TASK|VALUE = task14
CUSTOM_CELL_DENSITY|VALUE = 0.45
CUSTOM_CELL_SS|VALUE = NO
[download]

'lfr_task62_bunch_rpl' and 'aaa_task14_bunch_rpl' have the same content:

# Select fund
FUND|VALUE = mmi

# Select bank
BANK|VALUE = citi

# Select cell name
TASK_CELL_NAME|VALUE = lfr

# Select task
TASK|VALUE = task62

# Select task version
TASK_VERSION|VALUE = 1.0.9.0

# Select fund type
FULL_ESD|VALUE = MUTUAL

# Select customer premium
CUSTOM_CELL_SS|VALUE = YES

# Select customer brand density
CUSTOM_CELL_DENSITY|VALUE = 0.76

# Select card chip
CHIP_PKG_TYPE|VALUE|VALUE = OUTLINE
[download]

Mine has a different result, doesn't print the last two lines, like yours. Very strange, I will look into this. Thanks for your time.

open(REPLAY_FILE, "+<$rpl")
[download]

open my $REPLAY_FILE, '+<', $rpl or die $!;
while (my $line = <$REPLAY_FILE>) {
  #... do stuff with $line
}
close $REPLAY_FILE;
[download]

Sure -thanks for the tip.