My assumption was that there is only one match based on the OP's comment that print would work ok and that he wanted to assign to scalar as map would only return one value. If this assumption is incorrect, then one needs to change the approach.

In order to clarify some of the arguments in the thread and based on the assumption of only one match, please have a look at the following list of experiments: 

use strict;
use warnings;

my @match = map { /(2)/ ? $1 : () } 0..9;
print scalar @match, "\n"; # is 1, no grep required

@match = map { /(2)/ } 0..9;
print scalar @match, "\n"; # is 1

@match = map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 10

@match = grep { defined } map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 10

@match = grep { length } map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 1

[download]

From this I would conclude that the easiest-to-write version for the OP is indeed 

my ($val) = map { /^\*\s\(?([^\)]+)\)?/ } @GET_STRING;

[download]

not considering any performance issues. If there is more than one match, this just returns the first one, which might or might not be ok.

The whole discussion highlights that sometimes the best thing to do might be to use a for loop and be done with it. Probably the fastest solution here as well depending on the data: 

my $val;
for (0..9) {
    if( /(2)/ ) {
        $val = $1;
        last;
    }
}

[download]

In reply to Re^3: Assign result of map to scalar variable by hdb
in thread Assign result of map to scalar variable by ram31

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