### file.pm
sub funcC {
}
sub funcD {
}
sub funcE {
}
1;

### main script
#!/usr/bin/perl

use strict;
use warnings;
use Devel::Symdump;

sub funcA {
}
sub funcB {
}

sub get_functions {
    return Devel::Symdump->functions("main");
}

my %before = map {$_ => 1} get_functions();

require 'file.pm';

print "$_\n" for sort grep !$before{$_}, get_functions();

__END__
main::funcC
main::funcD
main::funcE