sub fred {
    open(FH, "< f.tmp") or die "open error f.tmp";
    # ... process file here
    die "oops";   # if something went wrong
    close(FH);
}
eval { fred() };
if ($@) { print "died: $@\n" }
# Update: this is better, see: [id://11130946]
# my $ok = eval { fred(); 1 };
# if (!$ok) { print "died: $@\n" }

# oops, handle FH is still open if exception was thrown.