#!/usr/bin/perl

use strict;
use re 'eval';

my @keywords = qw/foo bar 12345 abcd/;
my ($string) = "foobarfoo1234523423412345abcdefsadfabc";
our %result;

my @regexen = map {
    qr/(?:(\Q$_\E))(?{$result{$+}++})/
} @keywords;

my $re = do {
    local $" = '|';
    qr/@regexen/;
};

my @match = $string =~ /$re/g;

print "$_: $result{$_}\n" for @keywords;