Use -e to check if a file/dir exists. Then -d to check if it is a directory. You do not really need the -e, but it's nice to know.

#!/usr/bin/perl -w
use strict;

my $dir = '/etc';

if (-e $dir and -d $dir) {
    print "SPOON :)\n";
} else {
    print "spork :(\n";
}
[download]

You should really pick up "Programming Perl" it is explained in there. It is also under 'perldoc -d'

grep

grep> cd pub 
grep> more beer