> But I believe your example is also for "all distinct letters", it isn't clear to me how you'd use it for BernieC's templates.

I find the wording "template" confusing and thought it's about constructing a complicated regex by templates, i.e. like it's done with HTML.

If "template" is supposed to mean character class $chars = "abc.." whose chars are never repeated anywhere in the string, a negated approach is probably the simplest

$str !~ / ([$chars]) .* \1 /x

edit

use v5.12;
use warnings;

my @words = qw"abc aab abb aba abcd abca";

my $chars = "ad";

for (@words) {
    say "$_"
        if $_ !~ / ([$chars]) .* \1 /x
}

[download]

abc
abb              # NB: b wasn't in chars
abcd

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re^3: Nonrepeating characters in an RE (simple) by LanX
in thread Nonrepeating characters in an RE by BernieC

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