my $string = 'abcdefgxxabcdefgzzabcdsjfhkdfab';

my %seen;
1 while $string =~ /(\w{2,}?)(?{$seen{$1}++})(?!)/g;

print [sort {
           $seen{$b}  <=> $seen{$a}
        || length($b) <=> length($a)
    } keys %seen]->[0];

[download]
Update: Thanks Athanasius for your appreciation && corrections.

In reply to Re: RegEx + vs. {1,} by trizen
in thread RegEx + vs. {1,} by Sewi

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