Is line 7 (now commented out) what you referred to?
no error here on:
from perldoc perlvar
The variables $@, $!, $^E, and $? contain information about different
types of error conditions that may appear during execution of a Perl
program. The variables are shown ordered by the "distance" between the
subsystem which reported the error and the Perl process. They correspond
to errors detected by the Perl interpreter, C library, operating system,
or an external program, respectively.
To illustrate the differences between these variables, consider the
following Perl expression, which uses a single-quoted string:
open my $pipe, "/cdrom/install |" or die $!;
my @res = <$pipe>;
close $pipe or die "bad pipe: $?, $!";
After execution of this statement all 4 variables may have been set.
$@ is set if the string to be "eval"-ed did not compile (this may happen
if "open" or "close" were imported with bad prototypes), or if Perl code
executed during evaluation die()d . In these cases the value of $@ is
the compile error, or the argument to "die" (which will interpolate $!
and $?). (See also Fatal, though.)