If you mean simply putting a timeout on the read, then you can do it like this using the standard method for timeouts (alarm, $sig{ALRM}, die). I didn't actually test it, though.

my @pslist = ();
while (!@pslist) {
    local $SIG{ALRM} = { die "TIMEOUT" };
    my $pid;
    eval {
        alarm 5; # arrange for a wake-up call in 5 seconds
        
        $pid = open(PSLIST, " ssh -2 $user\@ $peer ./pslist | ")
            || die "Remote process list gathering error:\n$!.\n";

        while(<PSLIST>){
            chomp($_);
            push(@pslist, $_);
        }
        close(PSLIST);
        
        alarm 0; # clear the alarm, if we got this far ok
    }
    if ($@ =~ /TIMEOUT/) {
        # abort the attempt, and try again
        kill 'TERM' => $pid;
        @pslist = ();
    }
    elsif ($@) {
        die $@;
    }
}

foreach (@service){
    # .. check the existence of a process
}
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There is also at least one module on cpan for doing timeouts... but it's the sort of thing that is simple enough that you usually just wanna do it inline, rather than bringing in a module for it.