The following might be a good starter assuming the file is small enough to be slurped in (otherwise you'll want to loop over each line):

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

### slurp in the data into our scalar
my $data;
{
    local $/;
    $data = <DATA>;
}

### if you want to see all the matches
my @matches = ($data =~ m/matchingStuffHere[0-9]+/g);
print Dumper(\@matches),"\n";

### only pull the third token
my $third_token = ( $data =~ m/matchingStuffHere[0-9]+/g )[2];
print $third_token,"\n";

### pull the entire line that contains the third token
my $third_token_line = ( grep { m/matchingStuffHere[0-9]+/ } split($/,
+$data) )[2];
print $third_token_line,"\n";


### kindly donated from fortune
__DATA__
Do matchingStuffHere1 you suffer painful elimination?
Do you matchingStuffHere2 suffer painful recrimination?
Do you suffer painful matchingStuffHere3 illumination?
Do you suffer painful hallucination matchingStuffHere4?
In order to succeed matchingStuffHere5 in any enterprise, one must be 
+persistent and patient.
Saints should always be matchingStuffHere6 judged guilty until they ar
+e proved innocent.
By trying we can easily learn to endure adversity.  Another man's, I m
+atchingStuffHere7 mean.
[download]

I'm not sure exactly where you are going with this if you only want the third token (since you said the tokens are all the same). The preceding example code assumes the tokens are different so that it is easy to identify which one matched.