Definitely! I had this at one of my projects...

My face and all my hairs went pale, when I realized that a young colleague of mine called warn within $SIG{__WARN__}-handler.

As it turned out Perl was (since 5.8 IIRC) idiot proof. It locally resets signal handler redirections before calling them.

My colleague insisted that I exaggerated, because she "tested" (i.e ran) it once before committing into production.

Her warn did depend on an if clause and "production" meant a central module of a mod-perl environment...

UPDATE:

from warn

               Most handlers must therefore make arrangements to
               actually display the warnings that they are not prepare
+d to
               deal with, by calling "warn" again in the handler.  Not
+e that
               this is quite safe and will not produce an endless loop
+, since
               "__WARN__" hooks are not called from inside one.
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