It fails when you add adbc to @match_wanted. Easily fixed: 

use Math::Combinatorics qw( permute );

my @charset = qw( a b c );
my %valid = map { join( '', @$_ ) => 1 } permute( @charset );
my ($others) = map qr/[^$_]/, join '', map quotemeta, @charset;

sub match {
   my $s = shift;
   $s =~ s/$others//g;
   return $valid{$s};
}

[download]

or 

use Math::Combinatorics qw( permute );

my @charset = qw( a b c );
my ($valid) = map qr/^(?:$_)\z/, join '|', map quotemeta, map join('',
+ @$_), permute @charset;
my ($others) = map qr/[^$_]/, join '', map quotemeta, @charset;

sub match {
   my $s = shift;
   $s =~ s/$others//g;
   return $s =~ $valid;
}

[download]

or 

use Math::Combinatorics qw( permute );
use Regexp::List qw( );

my @charset = qw( a b c );
my ($valid) = map qr/^$_\z/, Regexp::List->new()->list2re(permute(@cha
+rset));
my ($others) = map qr/[^$_]/, join '', map quotemeta, @charset;

sub match {
   my $s = shift;
   $s =~ s/$others//g;
   return $s =~ $valid;
}

[download]

In reply to Re^2: REgular expression to check the string that allows "a","b" and "c" to occur only once in any order. (permutations) by ikegami
in thread REgular expression to check the string that allows "a","b" and "c" to occur only once in any order. by isha

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