package Foo;

use strict;
use warnings;
use warnings::register;

sub foo { print "Foo!\n" };

sub import {
  my $cur  = shift;
  my $dest = caller;

  for my $g (grep $cur->can($_),  @_) {
    warnings::warnif("sub '$g' already exists in $dest") and next
      if $dest->can($g);

    my($dest, $src) = map qualify_to_ref("$_\::$g"), $dest, $cur;
    *$dest = *$src;
  }
}

# This is what we need from Symbol to provide the qualify_to_ref function

my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT);

sub qualify ($;$) {
    my ($name) = @_;
    if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) {
	my $pkg;
	# Global names: special character, "^x", or other. 
	if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) {
	    $pkg = "main";
	}
	else {
	    $pkg = (@_ > 1) ? $_[1] : caller;
	}
	$name = $pkg . "::" . $name;
    }
    $name;
}

sub qualify_to_ref ($;$) {
    return \*{ qualify $_[0], @_ > 1 ? $_[1] : caller };
}

1;

__DATA__
Can't use string ("main::foo") as a symbol ref while "strict refs" in use at c:/Foo.pm line 39.

# test script

#/usr/bin/perl
use lib '/blah';
use Foo 'foo';
foo();