After going all around the houses playing with Win32::Process, Win32::Pipe and numerous other things, I finally arrived back at what I'm sure many others already knew. I wonder why they didn't speak up??

IPC::Open3 can do what you want.

#! perl -slw
use strict;
use IPC::Open3;
$|++;

sub timeout {
    my ($timeout, $output_ref, @cmd ) = @_;

    print "@cmd";

    my ($wtr, $rdr);
    my $pid = open3( $wtr, $rdr, $rdr, @cmd );
    print $pid;
    my $start = time();

    while( <$rdr> ) {
        push @$output_ref, $_;
        if (($start+$timeout) < time() ) {
            kill( 9, $pid) or warn $!;
            return 0; # Timeout. @$output_ref may contain some output.
        }
    }
    return -1; # Successful completion.
}

my @output;
if ( timeout(10, \@output, 'ping', '-t', 'bbc.co.uk') ) {
    print @output;
}
else {
    print "timed out...\n@output";
}
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As coded above, it will capture both STDOUT and STDERR from the child process and return it all to the caller. If you want to ignore the STDERR output use IPC::Open2, if you want the two seperated, it's a fairly trivial change. See the docs for details.