Rate substr_lval       subst     reverse substr_mod substr_copy
substr_lval  489949/s          --         -9%        -37%       -67%        -69%
subst        539218/s         10%          --        -31%       -63%        -66%
reverse      776376/s         58%         44%          --       -47%        -52%
substr_mod  1473954/s        201%        173%         90%         --         -8%
substr_copy 1606272/s        228%        198%        107%         9%          --