cmpthese(-3, {
    GrandFather => sub {
       local $_ = $test_text;
       scalar s/ ( +)/" " . (" " x length ($1))/ge
    },

    ikegami => sub {
       local $_ = $test_text;
       scalar s/(?<= )( +)/'&nbsp;' x length($1)/eg
    },

    Smylers => sub {
       local $_ = $test_text;
       scalar s/(?<= )( )/&nbsp;/g
    },
});

__END__
               Rate     ikegami     Smylers GrandFather
ikegami     22180/s          --        -25%        -31%
Smylers     29772/s         34%          --         -8%
GrandFather 32268/s         45%          8%          --