#!/usr/bin/perl -w
###################  Lists and Hashes Helping Each Other  ####################

#  Example:  Frequency of occurrence of each digit character.

while (print("Enter line: "), ($line = <STDIN>) !~ /^\s*quit\s*$/i)
{
      @digits = $line =~ /\d/g;
      foreach $digit (@digits)
      {
           $DigitFreq{$digit}++;
      }
}


foreach $digit (sort keys %DigitFreq)
{
     print "$digit:  $DigitFreq{$digit}\n";
}


#  Detecting the occurrence of something to prevent duplicates.
#  Example:  Getting all digit strings in input, putting in a
#  list, and preventing duplicates.

while (print("Enter line: "), ($line = <STDIN>) !~ /^\s*quit\s*$/i)
{
      @DigitStrings = $line =~ /\d+/g;
      foreach $number (@DigitStrings)
      {
           $DigitFreq{$number}++;
           push(@FinalStrings, $number) if $DigitFreq{$number} == 1;
      }
}


foreach $number (sort {$a <=> $b} @FinalStrings)  #  New kind of sort!!
{
     print "$number\n";
}
#########################  Sample Session Below  #######################
$ perl hash.demo.4a
Enter line: what 66 hello 098
Enter line: 6 what
Enter line: quit
0:  1
6:  3
8:  1
9:  1

Enter line: 99 bottles of beer on the wall, 99 bottles of beer
Enter line: take on down and drink it, 98 bottles of beer on
Enter line: the wall.  100 percent of 100 is 100.  I'm 50
Enter line: percent sure of that
Enter line: quit
50
98
99
100