Just uploaded Thread::Suspend to my personal CPAN directory. From the POD:

NAME
       Thread::Suspend - suspend and resume threads from another thread

SYNOPSIS
           use Thread::Suspend;             # exports suspend() and resume()
           use Thread::Suspend qw(suspend); # only exports suspend()
           use Thread::Suspend ();          # threads class methods only

           my $thread = threads->new( sub { whatever } );
           $thread->suspend;                # suspend thread by object
           threads->suspend( $thread );     # also
           threads->suspend( $tid );        # suspend by thread ID
           threads->suspend;                # suspend all (other) threads

           $thread->resume;                 # resume a single thread
           threads->resume;                 # resume all suspended threads

Unfortunately, this depends on Thread::Signal, so it currently only works on Linux.

Liz