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use 5.040;
use utf8::all; # utf8 @ARGV
# replacement for the pre-perl5.28 stringwise xor that worked on any codepoints (up to uvsize)
sub bitwise_xor {
# copy/stringize arguments so overload/magic only happens once per arg
my $a = "$_[0]";
my $b = "$_[1]";
if (!utf8::is_utf8($a) && !utf8::is_utf8($b)) {
no if $] > 5.022, 'feature' => 'bitwise';
return $a ^ $b;
}
if (length $a < length $b) {
$a =~ s/./chr(ord $& ^ ord($b =~ m!.!gs && $&))/gse;
return $a . substr $b, length $a;
}
else {
$b =~ s/./chr(ord $& ^ ord($a =~ m!.!gs && $&))/gse;
return $b . substr $a, length $b;
}
}
sub buddy_strings($string1, $string2) {
if ($string1 eq $string2) {
# a doubled character to "swap"
return $string1 =~ /(.)\1/s;
}
else {
return
# lengths must match
length $string1 == length $string2
# exactly 2 differing characters, adjacent
&& bitwise_xor($string1, $string2) =~ /^\0*([^\0])\1\0*\z/
# in opposite order in the two strings
&& substr($string1, $-[1], 2) eq reverse substr($string2, $-[1], 2)
}
}
sub main() {
my @inputs = @ARGV;
for my ($string1, $string2) (@inputs) {
printf "%-30s\n%-30s\n -> %s\n", $string1, $string2, (buddy_strings($string1, $string2) ? 'yes' : 'no');
}
}
main() unless caller;
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