This is the sort of thing I usually use for such purposes. Note this is recursive and therefore will search subdirectories also. :-)

#!/usr/bin/perl -w
# Recurse directories to find .txt files

use strict;
use File::Find;

my $file = '';
my $dir  = '';

@ARGV = qw(.) unless @ARGV; # current dir unless otherwise specified

$dir = shift @ARGV;

sub process_file {
           return unless -f;        #skip directories
           $file = $_;
           if ($file =~ m/\.(txt)/si) {
               # do stuff here
           } 
}

find(\&process_file, $dir);
[download]

HTH,

Update: Deleted a spurious line from the code. The original is from an example on recursive editing, and I stripped some (but not all) of the non-relevant code. Oops. ;-)