#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dumper;

# Filter out all words that can't be candidates one way or the other
my @candidates=grep { m{[RS]} } <DATA>;
chomp(@candidates);
# Sort them in order of length
my @orderedCandidates=sort{ length $a <=> length $b } @candidates;
# Push a guard on the end
push @orderedCandidates,"";

warn Data::Dumper->Dump([\@orderedCandidates],[qw(*orderedCandidates)]
+),' ';

my %hash;
my $length=length($orderedCandidates[0]);
for my $word (@orderedCandidates) {
    if (length($word) == $length) { # Same length ... add it to the ha
+sh
        $hash{$word}=undef;
         }
    else { # Hash is complete
        for my $Rword (grep { m{R} } keys %hash) { # Word has a R
            my $pos=0;
            while (($pos=index($Rword,'R',$pos)) >= 0) { # Found an R
                # Make its S equivalent
                my $Sword=$Rword;
                substr($Sword,$pos,1)='S';
                print "$Rword - $Sword\n"
                    if (exists $hash{$Sword});
                $pos++
                 }
             }
        # Done with this hash --- so start over
        %hash=(); $hash{$word}=undef;
        $length=length($word);
         };
     }

__DATA__
ONE
THREE
FOUR
FOUS
RRRRRRRR
RSRRRRRS
RRSRRRRR

[download]
which yields 
FOUR - FOUS
RRRRRRRR - RRSRRRRR

[download]
Just for fun I modified this replacing R by each of the letters of the alphabet and S by another (using english-words.95 (~ 220,000 words). The R <=> S exchange is the most common with 381 words and the J <=> Q is the least common with only 5 words. Elapsed time for the run 344.65 seconds.

In reply to Re: Comparing Lines within a Word List by clueless newbie
in thread Comparing Lines within a Word List by dominick_t

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