#!/usr/bin/perl -w
# author, date, revision, etc.

# This program will process user input with two functions.
# Command-line arguments will be treated as input file sources.
# No flags are allowed.

# modules used: none
# pragmas used: strict
use strict;

# function A: return a parameter with the letters reversed
# accepts only one scalar argument by prototype
sub A($)
{
  my $word = shift @_; # get the parameter

  # split the word into a list of letters with the split function, then
  # reverse the list with the reverse function, then
  # join the list letters into a scalar word, and return that word
  return join '', reverse split //, $word;
}

# function B: return true if a word is in the /etc/hosts file
# accepts only one scalar argument by prototype
sub B($)
{
  my $word = shift @_; # get the parameter
  my $hosts;
  # open the /etc/hosts file, or fail with message
  open HOSTS, '/etc/hosts' or die "Couldn't open /etc/hosts";
  # read the entire contents of the file into the $hosts variable
  read HOSTS, $hosts, -s HOSTS;  
  close HOSTS;
  # return whether the $hosts variable contains the parameter word anywhere
  # note that this will accept words like "om" for yahoo.com - word bounds
  # are not used
  return ($hosts =~ m/$word/);
}

# main loop: go through input lines, passing each word to B
# and, if B returns false, to A

my $word;				# will hold each word found

while (<>)
{
  chomp;				# eliminate trailing newlines
  foreach $word (split)			# split the line into words
  {
    if (B($word))			# if the word satisfies B
    {
      print "=B= word found: $word\n";	# print out the plain word
    }
    else				# the word is not ok for B
    {
      # print out the word, followed by its A() interpretation
      print "=A= word found: A($word) = ", A($word), "\n";
    }
  }
}

__END__
=head1 NAME

=head1 SYNOPSIS

=head1 DESCRIPTION

=head1 Author

=head1 Last Revision

=cut