Kindly help me to write a perl programme in this regard.

1. Construct a detailed specification of the problem.
2. Design an algorithm to fit the specification.
3. Write Perl code to implement the algorithm.
4. Write a test suite against the specification to prove that it has been met. (Once you become more proficient at this it is advisable to write the tests before the implementation.)
5. Document everything.

Use strict and warnings always. Read perlintro for the basics and then the other relevant parts of the documentation. Post back here with details if/when you get stuck.

Happy landings!

Now that you have edited your original post and it is readable, consider that is auspicable to present what you have already written to achieve your goal: infact many monks are not so propense (and with reason!) to answer back with complete, working code when no effort is shown by the original poster.

That said it usually help to have a procedure in plain english and then translate it to Perl as for your grade of experience: infact is not useful have back answers you are not ready to understand.

Looking at you data (and your title) it seems that you want to capture lines between a start one and and end one. This can be accomplished via the flip-flop operator: see range operators in perlop.

This funny named operator is bistable: id est it acts like a switch on and off. Consider the following example:

perl -e " foreach (1..$ARGV[0]){ print qq($_\n) if $_ == 5 .. $_==7}  
+" 15

5
6
7
[download]

The if part is true after a 5 (included) is encountered and remains true until a 7 (included) is reached.

So you can parse your data using a flip flop adjusted to your needs and for these lines strip out the unnecessary parts and print what it reamis join -ing them with the char you want.

Remeber to use strict and use warnings to play with a safe net!

L*

PS: see also flip flop at my homenode

L*

#!/usr/bin/perl -w 
open IN, "data";
while(<IN>)
    {
    Array having all the sample list (ie. 123, 124, 125)
    
    }
[download]

#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1180437

use strict;
use warnings;

$/ = "sample_end\n";

print join ' | ', map { join '!', /sample_char = (.*)/g } <DATA>;

__DATA__

sample = 123

sample_sub = info

sample_char = abc

sample_char = abc1

sample_char = abc2

sample_end

sample = 124

sample_sub = info

sample_char = bbc

sample_char = bbc1

sample_char = bbc2

sample_end

sample = 125

sample_sub = info

sample_char = cbc

sample_char = cbc1

sample_char = cbc2

sample_end
[download]

See How do I post a question effectively?

I formatted my post. Thank you for your concern

1. Read the line one by one from input file. You have to read more on 
+how to read input files in perl. 
2. If the line matches word sample_char, then split it based on = and 
+take the second part. You have to read more on regular expression and
+ split functions to implement this. 
3. Store the second part in an array.
4. Once all the lines are completed, display the output from array
[download]

#!/usr/bin/perl -w

open IN, "data";

while($file=<IN>)

{

@line = split(/ \= /,$file);

if ($line[0] =~ m/^sample$/g)

{

@sample = $line[1];

foreach (@sample)

{

print @line; unable to proceed from here

}

}

}

#!/usr/bin/perl
use strict;
use warnings;

my @finalArray = ();
while(<DATA>){
        if ($_=~/^sample_char/){
        my @line = split(/\=/,$_);
        #push (@finalArray, $line[1]);
        push @finalArray, $line[1];
       }
}
print "Final data ::  @finalArray";

__DATA__
sample = 123
sample_sub = info
sample_char = abc
sample_char = abc1
sample_char = abc2
sample_end
sample = 124
sample_sub = info
sample_char = bbc
sample_char = bbc1
sample_char = bbc2
sample_end
sample = 125
sample_sub = info
sample_char = cbc
sample_char = cbc1
sample_char = cbc2
sample_end
[download]

OUTPUT

Final data ::   abc
  abc1
  abc2
  bbc
  bbc1
  bbc2
  cbc
  cbc1
  cbc2
[download]

What code have you already written and how does it fail to do what you want?