my_prog.pl
----------
use A
use B
if <arg1> {
A.just_print("hi")
}else if <arg2> {
B.just_print("hello")
}

sub main_print(){
print @_;
}

A.pm
----
package A
sub just_print(){
print @_;
main::main_print(); <-- error
}
B.pm
----
package B
sub just_print(){
print @_;
main::main_print(); <-- error
}