cpanm --look Net::Pcap

##</code><code>##

sub have_functions {
    my @funcs = ();
    print "detecting available functions... ";

    my @paths = DynaLoader::dl_findfile(qw(-lpcap));
    my $libref = DynaLoader::dl_load_file($paths[0]);

    for my $func (@_) {
        my $symref = DynaLoader::dl_find_symbol($libref, $func);
        push @funcs, $func if defined $symref
    }

    print "ok\n";
    return @funcs
}

...

# Check that '-lwpcap' exports 'pcap_open_live'
print have_functions('pcap_open_live');


##</code><code>##

sub have_functions {
    my @funcs = ();
    print "detecting available functions... ";

    my @paths = DynaLoader::dl_findfile(split /\s+/, $options{LIBS});
    die "Couldn't find any library file satisfying '$options{LIBS}'"
        unless @paths;
    my $libfile = $paths[0];
    
    # On Win32, we assume that the lib file will not be statically linked
    # but will be a thin wrapper for a similarly named .dll file.
    # This is not universal but works in many cases
    # This assumes that a library -l$foo will map to lib$foo.a
    # through DynaLoader. We then try to find and load $foo.dll in $ENV{PATH}
    if ($has_Win32) {        
        (my $dll = basename $libfile) =~ s/\.\w+$//;
        $dll =~ s/^lib//;
        $dll .= '.dll';
        
        ($libfile) = grep { -f } map { File::Spec->catfile($_,$dll) } File::Spec->path;
        die "'$dll' not found in PATH"
            unless $libfile;
    };
    warn "Using '$libfile' as potential symbol candidate";

    my $libref = DynaLoader::dl_load_file($libfile);
    warn "Couldn't load $libfile via DynaLoader ($^E)"
        unless $libref;
    for my $func (@_) {
        my $symref = DynaLoader::dl_find_symbol($libref, $func);
        push @funcs, $func if defined $symref;
        #print "$func", $symref ? "" : " NOT", " found\n";
    };

    print "ok\n";
    return @funcs
}