The AM has one reasonable solution, but it assumes that the only failure mode that the $nofile variable applies to is the case where the file is not readable at the time it is tested.

• There is a race condition between the test and the open call, and
• the file may fail to open for other reasons.

If you can live with those conditions, great. Otherwise, another solution (similar to yours) might be:

my $nofile;
my $reason;
my $tempfile = "$tempdir/$ENV{'REMOTE_ADDR'}";
my @tmpfile;
if ( open( my $temp_fh, "<", $tempfile ) ) {
    @tmpfile = <$temp_fh>;
    close( $temp_fh ); # You don't need this, $temp_fh should be limit
+ed in scope
}
else {
    $nofile = 1;
    $reason = $!; # update: original typo == $@
}
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