Just giving you an idea

Assuming you files are text files

#!/usr/bin/perl
use strict; 
use warnings; 
my $dir_path="Your Directory Path"; 
opendir (DIR, $tmp_dir) or die $!;
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2.Open the destination file with the appending modeopen() function

open (MYFILE, '>>data.txt');
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3.Reading each files using the readdir function. readdir returns the name of each file or directory in the opened directory in turn when used in scalar context, or a list of the names of all files and directories in that directory when used in list context.

while (my $file_name = readdir(DIR)) {print "$file_name\n";}
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4.Within this loop open each file in read mode and do another loop to each all the content and check for whatever the word match you need with regular expression. If matches write that content into the "data.txt" file as  print MYFILE $file_content; Once each file completes close each file respectively  close (MYFILE);

use the function closedir function to close the opened directory