Debugging perl, breakpoint at specific file

[grimbys]

Hi! I want to use perl' debugger. How can I enable a breakpoint at other file that isn't principal?

I'm look for a sentence like:

b my_file#no_lin

(by default it is only possible at current file, isn't?)

I know I can :
b postpone my_subr
It is the more similar I could find, but I would like go to a line at this routine directly, without two break points.

(Note that I'm using emacs editor)
And, ... other question ...
(from perldebug)
What does 'Breakpoints may only be set on lines that begin an executable statement' is mean?

I don't understand why some times I recived a message that says me "Line x not breakable".

I found a example:
1 while (0)
2 {
3 ;
4 }
5 @a = "b";

<DB> b 5
<DB>
# It's ok

1 while (0)
2 {
3 ;
4 }
5 @a =
6 &quot;b&quot;;
<DB> b 5
Line 5 not breakable
# I don't understand, but I read from
#

http://world.std.com/~aep/ptkdb/

(Known problem section):
# ... That is where the operation is 'syntactically'
# completed ... well I conformed with b 6 ...

1 while (0)
2 {
3 ;
4 }; # this ';' is the change
5 @a =
6 &quot;b&quot;;
<DB> b 5
<DB>
# Now it is a breakpoint correct, why???

I'm having problemes debugging perl, so I ask you.
Thanks you