my @np = `ps aux | grep "/home/shekar/myscript.pl" | grep -v grep`;

print "Number of running processes: " . (scalar @np) . "\n"; 

##</code><code>##

my $np = 
   `ps aux | grep "/home/shekar/myscript.pl" | grep -v grep | wc -l`;
chomp $np;
print "Number of running processes: $np\n";