use Benchmark qw/:all :hireswallclock/; my $DATA = '01 fines name 2222 -P sws -1 reee.tee rrt'; cmpthese(-10, { 'rjt' => q{ $_ = $DATA; s/ (?=.*\s?-1 )/,/g; }, 'pushtaev' => q{ $_ = $DATA; my ( $left, $right ) = split /-1/, $_, 2; $left =~ s/ /,/g; join '-1', $left, $right; }, });