Lets use that in an example...

my @array = qw(foo bar food foofighters kung-foo);
my $count_foo = grep (/foo/, @array);
print "$count_foo\n";
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Prints "4" - which may or may not be what the OP was after (I suspect not).

my $count_foo = grep { $_ eq 'foo' } @array;
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..might be more what the OP was looking for.

Cheers,
Darren :)