% perl -del

Loading DB routines from perl5db.pl version 1.33
...
  DB<1> use LWP::UserAgent

  DB<2> l LWP::UserAgent::new
Switching to file '.../lib/LWP/UserAgent.pm'.
31      {
32          # Check for common user mistake
33:         Carp::croak("Options to LWP::UserAgent should be key/value pairs, no
t hash reference")
34              if ref($_[1]) eq 'HASH';
35
36:         my($class, %cnf) = @_;
37
38:         my $agent = delete $cnf{agent};
39:         my $from  = delete $cnf{from};
40:         my $def_headers = delete $cnf{default_headers};

  DB<3> l 30
30      sub new

  DB<4> b LWP::UserAgent::new

  DB<5> L
.../lib/LWP/UserAgent.pm:
 33:        Carp::croak("Options to LWP::UserAgent should be key/value pairs, not hash reference")
   break if (1)

  DB<6>