Answer.

Perl was originally designed as a scripting language for system administration, so the traditional error handling model was more procedural. However, over time extended techniques for handling exceptions and errors appeared in the language.

Background

In the first versions of Perl, errors were caught through function return values and checking the global variable $!. Later, eval constructs (dynamic capture) appeared, and modules like Try::Tiny added concise, safe try-catch patterns.

Problem

Standard Perl does not have built-in try-catch syntax. Errors can arise in both Perl code and external calls (for instance, file openings). If errors are not handled explicitly, the program may continue operating in an unpredictable state. It is necessary to wisely choose the error-catching technique depending on the context, complexity of the application, and reliability requirements.

Solution

For capturing errors in Perl, the eval function is used, wrapping potentially dangerous code in a block and analyzing the content of $@ after execution.
The die function is used to create custom errors. More specific error generation and re-raising of already described exceptions can be done using the sinon framework.
For "human" error handling, it is convenient to use third-party modules (for example, Try::Tiny).

Code example — error handling through Try::Tiny:

use Try::Tiny;

try {
    open my $fh, '<', 'file.txt' or die "Can't open file: $!";
    while (<$fh>) {
        print $_;
    }
}
catch {
    warn "An error occurred: $_";
};

Key Features:

The error mechanism is asynchronous — errors within eval and try/catch do not alter the main execution flow until explicitly handled.
Error catching is possible at different levels — low-level die/warn/return or high-level try/catch in modules.
Modules help to avoid typical pitfalls with eval, related to the overwriting of $@ and scope traps.

Trick Questions.

In what case will the eval block not catch a system error?

Eval does not always catch an error if a fatal exit occurs within C libraries (for example, SEGFAULT from XS code). Eval works only with Perl fatal errors, not with crashes of C extensions.

What happens to the variable $@ in nested eval blocks?

If another eval is called inside an eval, the value of $@ will be overwritten upon exit. Therefore, it is advisable to save $@ in a separate variable before the next eval to avoid losing the original error.

Why do auxiliary modules like Try::Tiny declare the variable $@ locally within catch/try?

Because Perl automatically clears $@ only on successful exit from try (eval). Returning on an error, next, or last can leave $@ uncleaned, leading to a "phantom" error in the following code. Modules like Try::Tiny create a scope-local variable specifically for this purpose.

Example:

try {
    die "Boom!";
}
catch {
    print "Caught: $_
"; # $_ - error trap inside catch
};

Typical Errors and Anti-Patterns

Ignoring the value of $@ after eval (error unnoticed).
Mutating $@ between multiple evals without saving.
Using simple die without try/catch for critical operations.
Lack of error logging.
Attempt to catch errors unrelated to Perl (for example, OS signals).

Real-Life Example

Negative Case

In the data export handler, an error while connecting to the DB is caught through eval, but the value of $@ is not saved, and logging is not performed. When another error occurs in the following eval, the first is completely lost.

Pros:

The code does not crash immediately in case of an error and continues to operate.

Cons:

It becomes impossible to understand during debugging why the export is not working, there is no error message.
There may be duplicate or false errors.

Positive Case

Using Try::Tiny for handling critical sections, all errors are recorded in a separate log, the original error is saved, and correctly displayed on the screen.