G'day BernieC,

I considered a solution using List::Util::uniqstr(). Unfortunately, your OP is somewhat ambiguous: you first say 'the *template* that says "these letters should be distinct"'; then you say 'my "template" might look like this: "abcdefa"' (where, with two 'a's, the letters are not distinct). I've provided two solutions; hopefully, one of them does what you want.

[Caveat: uniqstr first appeared in List::Util v1.45; the first stable Perl version with that version of List::Util is v5.26; if you have an older version of Perl, you can get a newer version of List::Util from CPAN.]

Solution 1 (pm_11146148_uniq_str_chars.pl):

#!/usr/bin/env perl

use strict;
use warnings;

use List::Util 1.45 'uniqstr';
use Test::More;

my @tests = (
    [abcdefa => 0], [abcdef => 1], [xyz => 1], [zzz => 0],
);

plan tests => 0+@tests;

for my $test (@tests) {
    my ($str, $exp) = @$test;
    is length($str) == uniqstr(split //, $str), !!$exp;
}
[download]

Output:

$ ./pm_11146148_uniq_str_chars.pl
1..4
ok 1
ok 2
ok 3
ok 4
[download]

Solution 2 (pm_11146148_uniq_str_chars_2.pl):

#!/usr/bin/env perl

use strict;
use warnings;

use List::Util 1.45 'uniqstr';
use Test::More;

my @tests = (
    ['abc', abcdefa => 0],
    ['def', abcdefa => 1],
    ['abc', abcdef => 1],
    ['xyz', xyz => 1],
    ['xyz', zzz => 0],
    ['xy',  zzz => 1],
);

plan tests => 0+@tests;

for my $test (@tests) {
    my ($tmpl, $str, $exp) = @$test;
    my %tmpls = map +($_ => 1), split //, $tmpl;
    my @chars = split //, $str;
    my @tmpl_chars = grep exists $tmpls{$_}, @chars;
    is 0+@tmpl_chars == uniqstr(@tmpl_chars), !!$exp;
}
[download]

Output:

$ ./pm_11146148_uniq_str_chars_2.pl
1..6
ok 1
ok 2
ok 3
ok 4
ok 5
ok 6
[download]