Getting all possible string combinations with Perl

Question

Given a string for example 'rogerdavis' than it should convert it to 'rogerd@vis' or 'rogerdav!s' or 'rogerdavi$' or 'rogerd@v!$' and all possible combination and append it in a file. So basically have to convert 'a' to '@', 's' to '$' and 'i' to '!' and use all possible combinations. This is to be done in Perl.

Pseudocode

• Create a new file
• Calculate number of occurrences of a,A,s,S,i,I (or we can accept keyword only in small or in caps to simplify the switch case)
• Calculate total number of possibilities we can have by using formula of combinations For total number of possibilities we perform the job on hand of replacing character a ->@, s->$, i-> I
• add unique entry to the file

This is what came to my mind at first. Please help me because I know there's got to be an easy and simple way to do this thing:

1. Accept keyword in an array keyword[ ]
2. Calculate length of the array in length_of_keyword
3. Scan array keyword[ ] from left to right count =0; for(i=0; i }

4. Using count to calculate total number of possibilities

   total_poss =0;
   r= 1;
   new_count = count
   for (i = count; i > 0; i--)
   {
       // fact( ) will calculate factorial
       total_poss += fact(new_count)/(fact(r)*fact(new_count - r))  
       r++;
    }
   
   for (k=0; k<total_poss; total_poss++)
      copy array keyword[ ] in temporary array temp[ ];
      for (i=0; i< new_count; i++)
      {
   
          for (j = 0; j< lenght_of_keyword; j++)
          {
              if (temp[i] is equal to 'a' || 'A' || 's' || 'S' || 'i' || 'I' )
              {
                  switch (temp[j])
   
                      case i: tempt[i] = ! ;
                                 if ( modified array is equal to an entry in file)
                                     continue;
                                 else save in file; break;
                      case I: (same as above or we can have function for above code)
                    .
                    .// similarly for all cases
                    .
           }
       }
   }
   

Answer 1

I wanted to give List::Gen a whirl. This problem provided the perfect excuse!

---

use strict;
use warnings;
use List::Gen;

my %symbol = ( a => '@', A => '@',
               i => '!', I => '!',
               s => '$', S => '$', );  # Symbol table

my $string = 'rogerdavis';
my @chunks = split /(?<=[ais])|(?=[ais])/i, $string;

# Turn into arrayrefs for cartesian function

@chunks = map { $_ =~ /^[ais]$/i ? [ $_, $symbol{$_} ] : [ $_ ] } @chunks;

my $cartesian = cartesian { join '', @_ } @chunks;  # returns a generator

say for @$cartesian;  # or 'say while < $cartesian >'

---

Output

rogerdavis
rogerdavi$
rogerdav!s
rogerdav!$
rogerd@vis
rogerd@vi$
rogerd@v!s
rogerd@v!$