Some generic observations since I dont do webdev, mod_perl seems to be written in mostly XS.

perl -MData::Dumper -e
"print Dumper(\%main::);"
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The sub is simply not defined. Most normal modules have subs living in typeglobs . "*Apache2::ServerUtil::restart_count{CODE}" returns a ref to a sub. You can also use Devel::Peek's Dump() command if Data::Dumper isn't detailed enough. You are probably missing a "require Foo;" or "use Foo;" somewhere. In very rare cases, one piece of code, is monkey patching, or local()izing the glob or the glob's CODE slice, and removing the sub/xsub from view permanently or temporarily. In other rare cases modules use AUTOLOAD to bring a sub into existence the first time it is called.