#!/usr/bin/perl
use strict;
use warnings;

my @all_sentences;    ## initialized an array

my $sentence = "";
print "\n Type \"quit\" to quit or press ENTER to continue: ";
chomp( my $input = <STDIN> );

LOOP: while ( $input !~ m{^\bquit\b}i ) {

    # Input a sentence
    print "\n\n Please type the filename(.txt): ";
    chomp( my $filename = <STDIN> );
     
    next LOOP if $filename eq "";  # go back to LOOP if filename is empty 

    # open the file or exit
    open my $fh, '<', $filename
      or die "Cannot open file $filename: $!";    

    my $sentence = do { local $/; <$fh> };        ## slurp a file
    close $fh or die "can't close file: $!";

    # To remove white space & fullstop
    $sentence =~ s/\s|\.//g;

    print "\n Sentence: $sentence\n";

    # To count number of total letters
    my $total_letters = 0;
    $total_letters = length($sentence);
    print "\n Total letters in the sentence= $total_letters\n";

    # To store all sentences as elements in the array for further comparisons
    push @all_sentences, $sentence;
    print "\n Type \"quit\" to quit or press ENTER to continue: ";
    chomp( $input = <STDIN> );
}

print join "\n", @all_sentences;    ## a test to show you got all the file content

# To find the difference of letters between  pairs of sentences i.e.
# sentence1 & sentence2, sentence2 & sentence3,sentence1 & sentence3 etc.
# Find the difference of letters between any two sentences   # Line 37
#my $diff_letters =
# code
#? ??
#   ? ?;             # Line 38
#print"\n Difference of letters between sentence1 & sentence2=my $diff_letters\n
#Difference of letters between sentence2 & sentence3=my $diff_letters\n
#Difference of letters between sentence1 & sentence3=my $diff_letters\n\n\n";
# Print to a text file:
#my $output="Result .txt";      # Line 42
#open (my $fh,">",$output) or die"Can't open file '$output'.\n";# Line 43
#print $fh "\n Difference of letters between sentence1 & sentence2=$diff_letters\n";
#print $fh "\n Difference of letters between sentence2 & sentence3=$diff_letters\n";
#print $fh "\n Difference of letters between sentence1 & sentence3=$diff_letters\n\n";
#close $output;                 # Line 47
# exit the program
#exit;