The question is: it is easy to have an eval succeed (hence setting $@ and return undef, but is it possible to have a failing eval to return a null $@?

Yes and no.

You cannot get $@ set to an actual null string. If you die with '' it will get the filename and line number info appended - just like any other die with a string sans trailing "\n".

As broquaint points out you can die with an error object that evaluates to false. However, this is (technically) not a null string.

If you really want to be sure an exception was thrown do:

if( ref($@) || $@ ne '' ) { ... handle exception ... }
[download]

But this is almost always overkill, unless you expect to be dealing with broken exception mechanisms. I've never come across a false exception that hasn't been a bug.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.