while (<>) {
   do_stuff_to $_;
}

or 

for (@ARGV) {
   do_stuff_to $_;
}

##</code><code>##

while (<*>) {
   do_stuff_to $_;
}

or better

opendir DH,".";
@dir=readdir DH;
closedir DH;

foreach (@dir) {
   Do_your_thing $_;
}

##</code><code>##

open (FH, ">/temp/tempfile");
print FH $temporary_data;

##</code><code>##

my $tempdir = "/temp/";
my $tempfile = "tempfile";

and then 

open FH "$tempdir$tempfile";