What is the difference between $@ and $! in Perl? Errors associated with eval are outputted using $@ . $! is also used for capturing the error. Then what is the difference between both of them?
13
votes
3 Answers
20
votes
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.
8
votes
$! is set when a system call fails.
open my $fh, '<', '/foobarbaz' or die $!
This will die outputting "No such file or directory".
$@ contains the argument that was passed to die. Therefore:
eval {
open my $fh, '<', '/foobarbaz' or die $!
};
if ( $@ ) {
warn "Caught exception: $@";
}
It make no sense to check $@ without using some form of eval and it makes no sense to check $! when you haven't called a function that can set it in the case of an error.
0
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