grep doesn't do what you think it does. For a start you're assigning the return value to a scalar, but it returns a list.

I think that what you want is something like this:

my @in = qw(bga cbga test);
my @out;
my @test = qw(bga);

foreach my $test (@test) {
  push @out, grep { /$test/ } @in;
}
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But I'm slightly worried by your phrase "exact pattern match". Perhaps what you really want is:

my @in = qw(bga cbga test);
my @out;
my @test = qw(bga);

foreach my $test (@test) {
  push @out, grep { $_ eq $test } @in;
}
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"The first rule of Perl club is you don't talk about Perl club."

It's not really what I like to do. I want to remove all exact matches which occur in @test out of the array @in. So the array @in should become (cbga test). With (grep s/($temp)/ /ig,@new_array) it removed all matches instead of exact matches so my array became (c test) instead of (cbga test).

You're not removing the elements, you're replacing them with spaces.

I think you want this, then:

my @in = qw(bga cbga test);
my @out = @in;
my @test = qw(bga);

foreach my $test (@test) {
  @out = grep { $_ ne $test } @out;
}
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Which leave @out contains all the elements from @in that don't exist in @test.

Actually, thinking about it, that's the disjunction of two sets and there's probably some really short recipe to do it in the Cookbook.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you don't talk about Perl club."

use strict;

my @array = qw (bga);
my @new_array = qw (bga cbga test);
my @tester;

print "@array\n";

# 
#foreach my $temp(@array) {
#    chomp($temp);
#    @tester = grep !/^$temp$/ig,@new_array;
#}

my $temp='('.(join'|',@array).')';
@tester = grep !/^$temp$/ig,@new_array;


print "@tester\n";
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