ok 1 - mca
       is mutating
       does not offend Perl::Critic
ok 2 - choroba
       is NOT mutating
       offends Perl::Critic
           Expression form of "grep" at line 6, column 5. See page 169 of PBP.
           Expression form of "map" at line 6, column 20. See page 169 of PBP.
ok 3 - tux
       is NOT mutating
       does not offend Perl::Critic
ok 4 - eplam
       is mutating
       does not offend Perl::Critic
           Rate   eplam choroba     mca     tux
eplam   41701/s      --     -2%    -40%    -54%
choroba 42626/s      2%      --    -39%    -53%
mca     69930/s     68%     64%      --    -23%
tux     91241/s    119%    114%     30%      --
1..4

##</code><code>##

use 5.14.2;
#use warnings;
no strict 'refs';
no warnings 'uninitialized';

use Perl::Critic;
use Test::More;
use Benchmark qw( cmpthese );

# Returns non-empty strings with leading and trailing spaces removed.
my %tests = (
    mca => <<'MCA',
sub mca # McA
{
    grep { $_ ne "" } map { s/^\s+//; s/\s+$//; $_ } @_;
    }
MCA
    tux => <<'TUX',
sub tux # Tux
{
    map { defined $_ ? m/(\S(?:.*\S)?)/ : () } @_;
    }
TUX
    choroba => <<'CHOROBA',
sub choroba # choroba
{
    grep !m/^$/ => map s/^\s+|\s+$//gr => @_
    }
CHOROBA
    eplam => <<'EPLAM',
sub eplam # eyepopslikeamosquito
{
    grep { !m/^\s*$/ && s/^\s*|\s*$//g } @_;
    }
EPLAM
);

my @orig = (" hello ", "\thello again\t", "", " ",
	 undef, " \t", "jock", "\t abc", "def \t ");
my @e = ("hello", "hello again", "jock", "abc", "def");
my @x;

# Configure Perl::Critic as you will:
my $critic = Perl::Critic->new(-severity => 4);

sub test {
    my ($name, $code) = @_;
    eval $code;
    @x = @orig;
    is_deeply ([ &$name(@x) ], \@e, $name);
    say "       ", (eq_array(\@orig, \@x) ? "is NOT mutating" : "is mutating");
    # Optional fixups that your Perl::Critic config expects
    $code = <<"FAKE_CODE";
package Foo;
use strict;
use warnings;
$code;
1;
FAKE_CODE
    say "       ", ($critic->critique(\$code) ? "offends Perl::Critic" : "does not offend Perl::Critic");
    print "           ", $_ for $critic->critique(\$code);
}

my %compare;
for (keys %tests) {
    my ($name, $code) = ($_, $tests{$_});
    test $name => $code;
    $compare{$name} = sub { @x = @orig; my @y = &$name(@x); };
}

cmpthese (1000000, \%compare);

done_testing;