$/ = \ 4096; # read in 4Kb blocks

foreach my $file (@filenames) {
    open (INFILE, "$file") || die ("Can't open file $file$!");
    while( <INFILE> ) {
        print OUTFILE1;
    }
}

##</code><code>##

{
    local @ARGV = @filenames;
    while( <> ) {
        print OUTFILE1;
    }
}