use strict; 
use diagnostics;
use warnings;

my $infile;
my @FILES = glob('file_*');
my $outfile = "outfile.csv";

open(OUTFILE, ">$outfile");

foreach $infile(@FILES){
	open(INFILE, "<$infile");
	while (my $line = <INFILE>){
		print OUTFILE $line;
		}	
	close INFILE;
}	

close OUTFILE;