Shell Programming and Scripting

line1
line2
Abs = {start marker}
line3
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B-1 = {end marker}
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line6

#!/usr/bin/perl -w

use strict;
use warnings;
use diagnostics;

print_inside(); 
print "\n";
print_outside(); 
 
sub print_inside {
     
    my $filename = 'text.txt';
    open(my $fh, '<', $filename) or die "Could not open file '$filename' $!";
    my $output = 0;
    
    while (<$fh>) {
        chomp;
        # print "$_ \n";
        
        if ( /Abs.*=.*{(.*)}/i ) {
            print "===S===> " . $1 . "\n";
            $output = 1;
        } elsif ( /B-1.*=.*{(.*)}/i ) {
            print "===E===> " . $1 . "\n";
            $output = 0;
        } elsif ($output) {
            print $_ . "\n"   
        }
        
    }
}

sub print_outside {

    my $filename = 'text.txt';
    open(my $fh, '<', $filename) or die "Could not open file '$filename' $!";
    my $output = 1;
     
    while (<$fh>) {
        chomp;
        # print "$_ \n";
        
        if ( /Abs.*=.*{(.*)}/i ) {
            $output = 0;
        } elsif ( /B-1.*=.*{(.*)}/i ) {
            $output = 1;
        } elsif ($output) {
            print $_ . "\n"   
        }
        
    }
}

 $ ./read.pl
===S===> start marker
line3
line4
===E===> end marker

line1
line2
line5
line6

@article{Test1:2011aa,
    Abs = {Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.},
    Author = {Lorem Ipsum and Ipsum Lorem},
    Date-Added = {2013-02-27 2:55:51 +0200},
    Title = {Geometric analogue of holographic reduced representation},
    Year = {2009},
    B-1 = {http://www.google.com}}

@book{Test2:2012bb,
    Abs = {Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.},
Author = {Lorem Ipsum and Ipsum Lorem},
    Date-Added = {2012-02-27 3:44:41 +0400},
    Year = {2010},
    B-1 = {http://www.google.com}}

@article{Test1:2011aa,
    Author = {Lorem Ipsum and Ipsum Lorem},
    Date-Added = {2013-02-27 2:55:51 +0200},
    Title = {Geometric analogue of holographic reduced representation},
    Year = {2009}}

@book{Test2:2012bb,
    Author = {Lorem Ipsum and Ipsum Lorem},
    Date-Added = {2012-02-27 3:44:41 +0400},
    Year = {2010}}

awk '!/^[ \t]+Abs/ && !/^[ \t]+B-1/' filename

awk ' $0 ~ /^[ \t]+Abs.*/  {
                next
} $0 !~ /^[ \t]+B-1.*/ {
                p = (p=="")?RS $0:p RS $0
} $0 ~ /^[ \t]+B-1.*/ {
                sub(/,$/,"}",p)
                print p
                p = ""
} ' file