foo.pl

use v5.10;
use re 'eval';

my @a = (
    [ 'aaa', sub { say 'Apple' } ],
    [ 'bbb', sub { say 'Banana' } ],
    [ 'ccc', sub { say 'Carrot' } ],
);

my @r = map {
    sprintf '%s(?{%d})', $a[$_][0], $_;
} 0 .. $#a;

my $r = '\G(?:' . join('|', @r) . ')';

my $i = 'aaabbbccc';

pos($i) = 3;

say "regex == /$r/";

$i =~ /$r/ or die "FAIL";

$a[$^R]->[1]->();