Re^3: How to print the lines immediately above and below a matching line?

[toolic]

Then you need to change your code. Something like:

my $data = <DATA>;
chomp $data;
if ($this_line =~ /\Q$data/)

[Bio90]

I have tried that but it has returned a "Use of uninitialised value $data". I do not understand - surely $data is initialised by my $data = <DATA>;?

[Anonymous Monk]

Show that code? Where did you add the line?

[Bio90]

Here is the code with the change

use strict;
use warnings;

open( my $fh, '<', 'input.txt') or die "Error opening file - $!\n";
open OUT, ">", "output.txt" or die "could not open output.txt $! \n";

my $this_line = "";
my $do_next = 0;
my $data = <DATA>;

while(<$fh>) {
    my $last_line = $this_line;
    $this_line = $_;
    
    chomp $data;
    if ($this_line =~ /\Q$data/) {
        print OUT $last_line unless $do_next;
        print OUT $this_line;
        $do_next = 1;
    } else {
        print OUT $this_line if $do_next;
        $last_line = "";
        $do_next = 0;
    }
}
close ($fh);

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