use strict;

my $FLG = 0;
my $OUTFILE = "result.log";

opendir(CURRENT, ".");
while (defined(my $dir = readdir(CURRENT))) {
    if ($dir =~ /(.*)\.txt/i) {
        if ($FLG == 0) {
            open(WRITE, ">>./$OUTFILE");
            $FLG = 1;
        }
        open(READ, "<$dir");
        my @data = <READ>;
        close(READ);
        print WRITE @data;
        print WRITE "\n";
    }
}
if ($FLG == 1) {
    close(WRITE);
}
closedir(CURRENT);