use strict;
use warnings;

my $prefix = 'P';

{
    my $first = 1;

    sub prefix_print {
        print $prefix if($first);
        print map {
            join($prefix, split(/^/,$_,-1));
        } @_;
        $first = $_[-1] =~ m/\n$/;
    }
}

prefix_print("A\nB","C\n");
prefix_print("A\nB");
prefix_print("C\n");