I'm surprised merlyn didn't point out the zap example from the original Programming Perl, but it is a little dated. :-)

More recently, there's Proc::Killall (alt.) (included with Proc::ProcessTable (alt.)) which let's you do ...

killall('HUP', 'xterm'); # SIGHUP all xterms
killall('KILL', '^netscape$'); # SIGKILL to "netscape"
[download]

    --k.