• Read the file line-by-line and use a state variable to remember when you are inside a block of interest.
• Read the file record-by-record by re-defining the $/ ($INPUT_RECORD_SEPARATOR) special variable.
• Read the file record-by-record by using Range Operators.

how to do something like "find this and since that delete next 4 lines and save the file"

Possible approaches:

1. Use an appropriate input record separator $/ (in your case, it looks like "ends here }\n" might work) and split the file into records that you then treat individually (as if they were separate files).
2. Use a so-called state machine, i.e. set/unset variables (depending on regex matches, for example) to represent the state that you're currently in while processing the file, such as state "line something starts here", or state "next block of something starts here", and then switch your processing of the lines accordingly.

1. Read the entire file into memory (for instance, into arrays), do all the slicing and dicing, and write out the result if you're done.
2. Read in the file part by part, write it back to a different file after the slicing and dicing. When done, rename the new file to the original.

A simple code snippet

#!/usr/bin/perl -w

use strict;
use warnings;


use constant HANDLER => {
        'line something starts here {' => sub{ return "Handler 1: do s
+omethig with this data\n".shift;},
        'next block of something starts here {' => sub{ return "Handle
+r 2: do somethig with this data\n".shift;},
        # Other record Handlers
};


# Read Records
while (my $line = <DATA>){
        chomp $line;
        next unless $line =~ /{/;
        my $header = $line; # READ HEADER

     
        # READ BODY
        $/="ends here }\n";
        my $body = <DATA>;
        chomp $body;
        $/="\n";

        print "Get Handler for: [$header]\n";
        my $output = &{HANDLER->{"$header"}}($body);

        print $output if $output;

}

__DATA__
line something starts here {
contains line 1
contains line 2
contains line 3
contains line 4
ends here }

next block of something starts here {
contains line 1
contains line 2
contains line 3
contains line 4
ends here }
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Hi, Thank you for your replies. And thank you for the code :). Anyway I will use it later when mine will be bad ;P. I've prepared something like:

my $array_position;
my $file = "/home/user/file.txt";

open FILE, $file;

my @file = (<FILE>);

close FILE;
foreach ( @file )
{
    if ($_ =~ /line 3/)
    {
        $array_position=$i+1;
        print "Position in array = ". $array_position. "\n";
    }
    $i++;
}

for ($a=$array_position-1; $a<$array_position+3; $a++)
{
    print "Postion ".$a." in the array = " .$file[$a];
}

@array = @file;
splice @array, 0, 'something';
print @array;
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The file.txt contains this:

line 1
line 2
fsefse line 3
line 4 ,...
line 5
line 6>
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The problem is it doesn't want to replace first element from the array to string I specified. Any ideas why ? Regards, Jarek

Is this what you want?

use strict;
use warnings;

use Data::Dumper;

my @file = (<DATA>);

my @array = @file;
splice @array, 0, 1,'something';
print Dumper \@array;


__DATA__
line 1
line 2
fsefse line 3
line 4 ,...
line 5
line 6>
[download]