You might want something like:

use warnings;
use strict;

my @pats = qw(ab ac ad ba bla etc);
my %pos;
@pos{ @pats } = 1 .. @pats;
my $re = join '|', @pats;
$re = qr/$re/;
while (<DATA>) {
    print "$1 $pos{$1}\n" if /($re)/;
}

__DATA__
fable
fact
[download]

Output:

ab 1
ac 2
[download]