#!/usr/bin/perl -w 
  
my %hash; 
  
open ( DATA, "<users.txt" ) or die "Can't open data file $!\n"; 
while ( <DATA> ){ 
        chomp; 
  
        my ( $user, $pw ) = split( /:/ ); 
  
        unless ( exists $hash{$user} ){ 
                $hash{$user} = $pw if $user; 
        } 
        else { 
                EXISTS : while ( each %hash ){ 
                        $user++; 
                        redo EXISTS if exists $hash{$user}; 
                        $hash{$user} = $pw; 
                        last EXISTS; 
                } 
        } 
} 
close DATA or die "Can't close data file $!\n"; 
  
for my $user (sort { $a <=> $b } keys %hash ){ 
        print "User: $user        Password: $hash{$user} \n"; 
}

#!/usr/bin/perl -w 
  
my %hash; 
  
open ( DATA, "<users.txt" ) or die "Can't open data file $!\n"; 
while ( <DATA> ){ 
        chomp; 
  
        # first, extract username/pw from line 
  
        my ( $user, $pw ) = split( /:/ ); 
 
  
        # now, if the username hasn't already been read, toss it into the hash 
  
        unless ( exists $hash{$user} ){ 
                $hash{$user} = $pw if $user; 
        } 
  
   
        else { 
                # this part will only be run if it's a duplicate username. 
                # we can't just increment it because we don't want to assume that 
                # simply incrementing it will make it unique. So we're going to   
                # loop through the keys of the hash to make sure it's not already  
                # defined. 
  
                # I like to use loop labels.  This makes it very easy to 
                # remember what's going on when you have to review the code 3 
                # months later, or if you're nesting loops.  Also note that 
                # we're using the redo and last, which makes labels necessary 
                # if loops are being nested. 
  
                EXISTS : while ( each %hash ){ 
  
                        # start off the loop with incrementing the username 
  
                        $user++; 
  
  
                        # if the incremented version exists, start again (note 
                        # that the username is still incremented) 
  
                        redo EXISTS if exists $hash{$user}; 
  
  
                        # if we've incremented the username to the point where 
                        # it's now unique, then the redo will not run and 
                        # we get to this point.  Assign the hash value and 
                        # last out of the loop. 
  
                        $hash{$user} = $pw; 
                        last EXISTS; 
                } 
        } 
} 
close DATA or die "Can't close data file $!\n"; 
  
for my $user (sort { $a <=> $b } keys %hash ){ 
        print "User: $user        Password: $hash{$user} \n"; 
} 
  
# now you have a hash that's propagated with unique usernames 
# as the key and the password as the key's value. 

#!/usr/bin/perl -w 
  
my %hash; 
  
open ( DATA, "< users.txt" ) or die "Can't open users.txt $!\n"; 
  
while ( <DATA> ){ 
        chomp; 
  
        # instead of assigning $user and $pw, we're going to assign only 
        # the username and place the remaining data in an array. 
  
        my ( $user, @data ) = split( /:/ ); 
  
        unless ( exists $hash{$user} ){ 
   
                # so now when the hash is propagated, we give it the value of 
                # the entire array (instead of the password only as in the  
                # previous example) 
  
                $hash{$user} = [ $user, @data ] if $user; 
        } 
        else { 
                EXISTS : while ( each %hash ){ 
                        $user++; 
                        redo EXISTS if exists $hash{$user}; 
  
                        # Same here 
                        $hash{$user} = [ $user, @data ]; 
                        last EXISTS; 
                } 
        } 
} 
  
close DATA or die "Can't close users.txt $!\n"; 
  
open ( NEW, "> usersnew.txt" ) or die "Can't open usersnew.txt $!\n"; 
for my $user (sort { $a <=> $b } keys %hash ){ 
  
        # Now all we need to do is dererence the hash value (the value 
        # which is everything that was in @data for each user). 
        # you could have also done: 
        # my @array = @{$hash{$user}}; 
        # and then you can treat the contents like a regular array. 
  
        print NEW join ( ";", @{$hash{$user}} ), "\n"; 
} 
close NEW or die "Can't close usersnew.txt $!\n";