Getting file and line number where a subroutine is declared

[Ovid]

Given a subroutine reference, is there a way to find out the file and line number where the subroutine was declared? warn and friends seems to get this right, but I need this externally. Here's my test program:

#!/usr/bin/perl -l

use strict;
use warnings;
use B;

# line 99 'bin/some_code.pl'
{
    no strict 'refs';
    print B::svref_2object(\*{'Foo::some_sub'})->LINE;
    print B::svref_2object(\&Foo::some_sub)->GV->LINE;
}
Foo::some_sub();

package Foo;
# line 23 'bin/some_file.pl'
sub some_sub {
    warn "Got to here";
}

That outputs:

102
102
Got to here at 'bin/some_file.pl' line 24.

The line information is not what I'm expecting, so I assume I'm doing something wrong (B::GV has a corresponding FILE method, but until I get LINE working, it's not much use to me).