How to look for exact pattern match

[juo]

How can I look for an exact pattern match. I would like to interrogate a pattern and remove exact matches out of the array which occur in another array. If I use (grep s/$temp/ /ig,@new_array) then it will remove all matches instead of exact matches. See example below. Any clues ?

use strict;

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

print "@array\n";

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

print "@new_array\n";

[davorg]

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;
}

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;
}

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

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

[juo]

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).

[davorg]

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;
}

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."

[arhuman]

Is the following code what you're looking for ?


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";


UPDATE :
Ooops davorg said it faster...
Furthermore if it's case-sensitive 'ne' is better than the regex used in my examples...

UPDATE2 :
Thanks Davorg for catching my error !
Only the last element of array will be taken out of the list,
as the @tester array is completly reconstructed at each step of the loop (only ok with one element ;-)
I've corrected the code with another solution...
But you'd definitly better use davorg's one.

"Only Bad Coders Code Badly In Perl" (OBC2BIP)