fromto

#!/usr/bin/perl
# print lines in a file between the <from> pattern and the <to> pattern
# usage: fromto <from> <to> <file>

use strict;
use warnings;
use Getopt::Long;

my $invert;
my $skip;
my $help;
my $result = GetOptions(
  "invert|v" => \$invert,
  "skip|s" => \$skip,
  "help|h" =>);

sub usage
{
	print STDERR "Usage: fromto [options] <from pattern> <to pattern> [<file>]\n";
	print STDERR "Options:\n";
	print STDERR "    -s    Skip the lines matching the patterns\n";
    print STDERR "    -v    Invert - print the opposite of normal\n";
	print STDERR "Notes:\n";
	print STDERR "          Reads from stdin if no file name is supplied\n";
	print STDERR "          Patterns are in Perl compatible regex syntax\n";
}

if (!$result)
{
	usage;
	exit 2;
}
if ($help)
{
	usage;
	exit 0;
}

my $from = shift @ARGV;
my $to = shift @ARGV;

my $started = 0;
my $skip_boundary = 0;

sub print_boundary {
  if ($invert) {
    print if $skip_boundary;
  } else {
    print if !$skip_boundary;
  }
}

sub print_middle {
  if (!$invert) {
    print;
  }
}

sub dont_print {
  if ($invert) {
    print;
  }
}

LINE:
while (<>) {
    if ($started) {
        if ($to && /$to/) {
            print_boundary();
			$started = 0;
			next LINE;
        }
        else {
            print_middle();
            next LINE;
        }
    }
    if (!$from || /$from/) {
        $started = 1;
        print_boundary;
        next LINE;
    }
    dont_print;
    next LINE;
}