package ECHO_MODULE;

sub say_hi {print "hi\n";}
sub say_bye {print "bye\n"}

package main;
print "enter subroutine name: ";
chop ($subname = <STDIN>);

if (ECHO_MODULE->can($subname) ) {
    ECHO_MODULE->$subname();
} else {
    print "sub '$subname' not defined.\n";
}