use strict;
use warnings;
use 5.010;
use List::Util qw(max);

my @letters = ('a' ... 'z', (' ') x 5);

my %words = map {
    join('', map { $letters[int rand(@letters)] } 1 .. max(5, rand(50))) => $_
} 1..5_000;

my @keys_sorted_by_length_desc  = sort { length $b <=> length $a } keys %words;

my $re = join '|', @keys_sorted_by_length_desc;
$re = qr{($re)}i;

while (<>) {
    chomp;
    if ($_ =~ $re) {
        say "found match $1 in '$_', $words{$1}";
    }

}