Instead of using ps and grep, why not use Proc::ProcessTable? If you're on one of its supported systems (and quite a few are supported), you can use it to parse the process table instead of the ps command. Then you could do (untested and probably wrong, since I have no access to this module):

use strict;
use Proc::ProcessTable;

sub is_running {
   my ($pattern) = @_;
   my $t = Proc::ProcessTable->new();

   foreach $proc ( @{ $t->table() } ) {
     $proc->cmndline() =~ /^$pattern/ and return 1;
   } 
   
   return 0;
}
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You might also want to take a look at Watchdog.

stephen