Re: how to check for a word in a file and if found remove that line, the above line and the below line from the file.

[ikegami]

my $prev = '';
my $skip_next = 0;
while (<>) {
   if (/XXXXX/) {
      $prev = '';
      $skip_next = 1;
   }
   elsif ($skip_next) {
      --$skip_next;
   }
   else {
      print($prev);
      $prev = $_;
   }
}

print($prev);

If you want to skip more than one line:

my $skip_before = 1;
my $skip_after  = 1;

my @prev;
my $skip_next = 0;
while (<>) {
   if (/XXXXX/) {
      @prev = ();
      $skip_next = $skip_after;
   }
   elsif ($skip_next) {
      --$skip_next;
   }
   else {
      push @prev, $_;
      print(shift(@prev)) if @prev > $skip_before;
   }
}

print(@prev);

One read. One check. Handles subsequent matching lines. Handles matches on the first line. Handles matches on the last line.