#!/usr/bin/perl
use 5.016;
use warnings;
use strict;
use Data::Dumper;
# 1021730

my @arr = ("ATOM 1276 CB ASP B 63 52.957 58.788 67.683 1.00 44.59 C",
    "ATOM 1280 N GLY B 64 52.075 55.496 66.522 1.00 35.29 N",
    "ATOM 1281 CA GLY B 64 51.005 54.534 66.322 1.00 32.64 C",
    "ATOM 1282 C GLY B 64 49.693 55.103 65.854 1.00 30.87 C",
    "ATOM 1283 O GLY B 64 48.630 54.545 66.092 1.00 27.93 O",
    "ATOM 1284 N LYS B 65 49.739 56.255 65.189 1.00 31.10 N",
    "ATOM 1285 CA LYS B 65 48.527 56.912 64.720 1.00 33.91 C",
    "ATOM 1286 C LYS B 65 48.629 57.147 63.216 1.00 32.04 C",
    "ATOM 1287 O LYS B 65 49.675 57.571 62.721 1.00 31.87 O"
    #Col1  2   3  4  5  6   7      8       9    10    11  12
    );

# So, let's say columns 3, 6, 7, 10 and 11 are the ones you want to select:

my ($selected, @selections);

for my $line(@arr) {
    if ( $line =~ /ATOM\s     # leading "ATOM" followed by a space -- e.g. Column 1
              \d{4}\s         # 4 decimal digits followed by a space (FBAS)
              ([A-Z]{1,2})\s  # CAPTURE to $1: One or Two UC letters FBAS from Col 3 
              [A-Z]{3}\s      # Three UC letters
              B\s             # "B" -- constant in example data at Col 5
              (\d\d)\s        # CAPTURE TO $2 exactly 2 digits from Col 6
              (\d+\.\d+)\s    # CAPTURE to $3: digit(s), decimal pt, digit(s) Col 7
              \d+\.\d+\s      # 1 or more digits, decimal pt, digits Col 8: 
              \d+\.\d+\s      # Col 9
              \d+\.\d+\s      # Col 10
              (\d\d\.\d\d)\s  # CAPTURE to $4 exactly 2 digits, decimal, 2 digits Col 11
              ([CNO]$)/x  )   # CAPTURE TO $5: one UC "C", "N", or "O" adjacent to EOL
            {
             $selected = $1 . " | " . $2 . " | " . $3 . " | " . $4. " | " . $5;
             say $selected;   # for DEMO and DEBUG only
             push @selections, $selected;
     }
     # .... and do whatever sleight-of-hand you need with  @selections...
}

say Dumper @selections;