TIMTOInterpretation (and I would never call you stupid ;-)

But I like this one, so:

use v5.12;
use warnings;

my $re = templ2regex("Mississippi");

for my $inp (qw/Mississippi Mossossoppo Miiiiiiippi/) {
    if ( my @matches = ( $inp =~ /$re/ ) ) {
        say "Match: $inp re: $re"
            if is_uniq(@matches);
    }
}

# Mississippi -> (.)(.)(.)\3\2\3\3\2(.)\4\2
sub templ2regex {
    my ($template) = @_;

    my ( $re, %grp, $cnt );

    $re .= $grp{$_} // do { $grp{$_} = "\\" . ++$cnt; "(.)" }
        for split //, $template;

    return $re;
}

# @_ elements all distinct?
sub is_uniq {
    my %uniq;
    @uniq{@_} = ();
    return @_ == keys %uniq;
}

[download]

=> 

Match: Mississippi re: (.)(.)(.)\3\2\3\3\2(.)\4\2
Match: Mossossoppo re: (.)(.)(.)\3\2\3\3\2(.)\4\2

[download]

if you really want to have it all in one regex, consider putting the uniq test into a (?{...}) block which does a *FAIL

Both are not canonical regexes but IMHO far better to maintain.

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

update

refactoring: better documentation and variable names

In reply to Re^2: Nonrepeating characters in an RE by LanX
in thread Nonrepeating characters in an RE by BernieC

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