perl to remove lines from file

Question

I have file that looks like:

ATOM 2517 O   VAL 160 8.337  12.679  -2.487
ATOM 2518 OXT VAL 160 7.646  12.461  -0.386
TER 
ATOM 2519 N   VAL 161 -14.431  5.789 -2         


        

Answer 1

use strict;
use warnings;
use Tie::File;

my @array;

tie @array, 'Tie::File', 'myFile.txt' or die "Unable to tie file";

my %unwanted = map  { $_ => 1 }                # Hashify ...
               map  { $_-1, $_, $_+2 .. $_+4 } # ... the five lines ...
               grep { $array[$_] =~ /^TER/ }   # ... around 'TER'  ...
               0 .. $#array ;                  # ... in the file

# Remove the unwanted lines
@array = map { $array[$_] } grep { ! $unwanted{$_} } 0 .. $#array;

untie @array;  # The end