Generally it helps us help you if you show the error generated by running the program.

It will also help you track down problems if you always use strictures (use strict; use warnings;). I appreciate the code shown may be a fragment of something larger, but just to make sure you are aware of a couple of coding techniques, here's a "tidied" version of your code:

use strict;
use warnings;

my $grepper = 'label("';
print "$grepper\n";

my @array = ("label(", "label");
my @LABEL = grep {/\Q$grepper\E/} @array;

print ">@LABEL<\n";
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Note the updated final print to make it clear that the array is empty.