It takes a little longer, but the result is a file that shows all words in your worlist which differ in one place only and they are sorted according to which characters are different.

For instance for "rs" differences, the result (based upon my wordlist) is as follows:

***** rs *****
    abaser - abases
    abater - abates
    abider - abides
    abjurer - abjures
    ...
    year - yeas
    yodler - yodles
    yummier - yummies
    zanier - zanies
    zoner - zones
[download]

And here is the program:

use Modern::Perl qw/2015/;
use List::MoreUtils qw/zip natatime/;
use autodie;

open( my $DICT, '<', './wordsEn.txt' ) or die "Could not open dictiona
+ry - $!";
my @dict;
print scalar <$DICT>; # show copyright message of word list

# step 1: sort the dictionary into bins per length of the word
while ( my $word = <$DICT> ) {
    chomp $word;
    next unless $word;
    push @{ $dict[ length $word ] }, $word;
}
close $DICT;

# step 2: for each bin look for words that differ in one place only
my %results;
for my $length ( 2 .. @dict - 1 ) {
    next unless $dict[$length]; # skip if no words of this length
    my @bin = @{ $dict[$length] };
    next if @bin < 2; # skip if only one word of this length
    say "*********** Testing words of length $length ***********";
    while ( my ( $index, $test ) = each @bin ) {
        for my $check ( @bin[ $index + 1 .. @bin - 1 ] ) {
            my $diff = $test ^ $check;
            if ( 1 == $diff =~ tr/\x00//c ) { # only one character dif
+ferent
                # find which characters are different
                my @first  = split '', $test;
                my @second = split '', $check;
                my @test = zip @first, @second;
                my $it = natatime 2, @test;
                while ( my @vals = $it->() ) {
                    next if $vals[0] eq $vals[1];
                    my $key =
                      $vals[0] lt $vals[1]
                      ? "$vals[0]$vals[1]"
                      : "$vals[1]$vals[0]";
                    push @{ $results{$key} }, "$test - $check"; # save
+ in hash
                    last;
                }
            }
        }
    }
}

say "Now writing results";
open( my $RESULTS, '>', './results.txt' ) or die "Cannot open output f
+ile $!";
for my $key ( sort keys %results ) {
    say $RESULTS "***** $key *****";
    for my $words ( sort @{ $results{$key} } ) {
        say $RESULTS "\t$words";
    }
}
close $RESULTS;
[download]

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