It is main::func_name.

Isn't it more accurate to say "It is main::func_name in that particular case", and that in the general case it is something like __PACKAGE__::func_name, where __PACKAGE__ is the package in which the function was defined?

>perl -wMstrict -le
"package Foo;
 print 'in package Foo';
 sub my_name { return (caller 0)[3] }
 print my_name();
 package main;
 print 'in package main';
 print Foo::my_name();
 sub my_name { return (caller 0)[3] }
 print my_name();
 package Foo;
 print 'in package Foo';
 print main::my_name();
 print my_name();
"
in package Foo
Foo::my_name
in package main
Foo::my_name
main::my_name
in package Foo
main::my_name
Foo::my_name
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