You need to find the node itself and then print out the literal value of that node using toString(). That will also print out the enclosing tags but simple regular expressions can strip them out:
my ($node) = $dom->findnodes('/doc/text');
my $string = $node->toString;
print "toString:\n$string\n";
# remove enclosing tags
$string =~ s/^<[^>]+>//;
$string =~ s/<[^>]+>$//;
print "toString:\n$string\n";
Output:
toString:
<text>From mobile, <ph1 i="1" type="33" x="1"/>dial<ph2 i="1"/> this n
+umber:</text>
toString:
From mobile, <ph1 i="1" type="33" x="1"/>dial<ph2 i="1"/> this number: