$ perl -Mstrict -Mwarnings -E '
    use Benchmark qw{cmpthese};

    my $x = q{1|2|3|||6|7||||};

    cmpthese(1e6 => {
        while_no_repeat => sub {
            my $line = $x;
            while($line =~ s/\|\|/\| \|/){}
        },
        just_repeat => sub {
            my $line = $x;
            $line =~ s/\|(?=\|)/| /g;
        }
    });
'
                    Rate while_no_repeat     just_repeat
while_no_repeat 158479/s              --            -21%
just_repeat     201613/s             27%              --