use strict;
use warnings;

my %searches =
(
    bar  => " bar  \n\n",
    bar1 => " bar1  \nw\n",
    baz  => "baz",
    foo  => "  foo  c  \n",
    foo1 => " foo ",
);

my $x;
my $regex = qr{ ^ \s* (??{ $x }) \s* $ }x;

for (sort keys %searches)
{
    $x = $_;
    print "$_: ", $searches{$_} =~ $regex ? 'match' : 'no match', "\n";
}