sub newfile_create {
$account_number = "12345";

$master_file = "/usr/local/foo/htdocs/master_file.txt";
open (IN, "$master_file") or die "Couldn't open file: $!"; 
$new_file_content = join("", <IN>);
close (IN);

# Note -- the 'master file' contains a variable, $account_number that needs to be substituted when the file contents are written into the variable, $new_file_content before writing this data into the $new_file_path location (file).

$new_file_path = "/usr/local/foo/htdocs/sub/file1.js";

open(IN, ">$new_file_path");
print IN "$new_file_content";
close(IN);

return;
}