There are several things that are not efficient in your script as shown in your OP.

1. why assign "matched" string before going over the string? Only to check it using an "eval" string.
2. You are chomping the string twice for what reason?
   Why not do:

   while (my $line=<DATA>) {
       chomp($line);..
   [download]

3. finally, you don't want to be using $&, $' and $` in your program.
   Check perlfaq6 on your system as perldoc perlfaq6
   OR check Here

#file: test.pl
#!/usr/bin/perl -w
use strict;
use v5.10;

my $pattern = qr/test/;

while (my $line=<DATA>) {
    chomp($line);
    $line =~ /($pattern)/p;

    my $result =  $line. '  => matched:'.${^MATCH}.$/;
    print $result;
}

__DATA__
test1a.txt
test1b.txt
test1c.txt
[download]