This is anagramming, and the nicest solution is well-known here. Split your string into characters, sort them, and rejoin them. Compare against a hash with keys made the same way from your dictionary or wordlist.

my %dict = do {
    open my $fh, '<', '/usr/dict/words' or die $!;
    map {chomp; join( '', sort split //, lc $_), $_} <$fh>;
};
my $canon = join '', sort split //, lc 'RTESAMCNA';
print $dict{$canon} if exists $dict{$canon};
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No regex or combinatorial excess needed.