My solution doesn't change the list, as it uses the /r modifier. 
#!/usr/bin/perl
use warnings;
use strict;

use Test::More;

sub trim_nonempties {
   ## no critic (ProhibitMutatingListFunctions)
   grep { !/^\s*$/ && s/^\s*|\s*$//g } @_;
   ## use critic
}

sub choroba {
    grep !/^$/, map s/^\s+|\s+$//gr, @_
}

my @X = ( ' hello ', "\thello again\t", '', " ", " \t", 'jock', "\t ab
+c", "def \t " );
my @changed = @X;
my @y = trim_nonempties(@changed);

my @stay = @X;
my @w = choroba(@stay);
is_deeply(\@y, \@w, 'same');
is_deeply(\@X, \@stay, 'no mutation');
done_testing();

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In reply to Re^2: Code review: function to trim whitespace from all items in a list by choroba
in thread Code review: function to trim whitespace from all items in a list by eyepopslikeamosquito

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