DB<100>  w $main::{"_<".(caller 3)[1]}[(caller 3)[2]] =~ /\bprint\b/
  DB<101> r
0
1
Watchpoint 0:	$main::{"_<".(caller 3)[1]}[(caller 3)[2]] =~ /\bprint\b/ changed:
    old value:	''
    new value:	'1'
main::(tst.pl:13):	print $x++;