Of course it's possible, just place a conditional in the grep.

$ perl -Mstrict -Mwarnings -E '
my @array = ( 12, -85, 36, -10, 75, -38 );
say qq{@array};
my @notNegatives = grep { $_ >= 0 } @array;
say qq{@notNegatives};'
12 -85 36 -10 75 -38
12 36 75
$
[download]

I hope this is helpful.