END { print "$_ => $INC{$_}" for sort keys %INC }
[download]

Or getting slightly fancy (but not foolproof)

package DumpPkgs;

use Filter::Util::Call;

sub import {
  my( $type ) = @_;
  filter_add( bless { } );
}

sub filter {
  my $self = shift;
  my $status;

  if( ($status = filter_read()) > 0 ) {
     print "Used $1\n" while /use\s+(\S+)/g
  }

  $status;
}
1;
[download]

You also could use the CPAN.pm autobundle command to generate a bundle of what's currently installed on the machine.