in reply to print a determinate line number

sorry if i think too simple, but did you mean you need to print whatever is on the 5th line ... $_ contains it ;)

if( $line_number == 5 ){
  print "Line $line_number contains this text:\n", $_, "\n";
}

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Re^2: print a determinate line number
by Paulux (Acolyte) on Oct 06, 2009 at 12:29 UTC
    Now I explain better my problem, I have to compare the text lines like this: the first with the second, the second with the third and so on and if the following line is different from the previous i have to print it.
[reply]
      if the following line is different from the previous i have to print it

      For that, you'd have to keep the previous line: 

      my $prev;
while (<>) {
    print if defined($prev) and $_ ne $prev;
    $prev = $_;   # update $prev
}

      [download]

      (The defined check would skip the first line, as there isn't really one previous to it...)

[reply]
[d/l]
[select]
      ah i see it now ;) ... something like this then. 
      use strict;
use warnings;

my $previous_line;

while(<DATA>){
  chomp;
  if($.==1){
    $previous_line = $_;
    next;
  }
  if($_ eq $previous_line){ print "Line $. : $_\n"; }
  $previous_line = $_;
}

__DATA__
a
b
b
c
c
c
d

      [download]
      UPDATE:

      Sorry the code above prints the duplicated lines, which is the opposite of what you wanted. i see that almut already has an elegant solution for you.

[reply]
[d/l]
        Thanx a lot, i have just added some control but it works.
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