use Benchmark qw( cmpthese );

use Inline CPP => 'DATA';

$main::string = '1234!' x 55e3;

sub cpp {
  my $copy = $main::string;
  my $ix = nth_index( $copy, '!', 50000 );
  substr( $copy, 0, $ix ) =~ tr/!/\n/;
  return \$copy;
}

sub regex {
  my $copy = $main::string;
  $myregexp::count = 0;
  $copy =~ s/!(??{ ( $myregexp::count++ < 50000 ) ? '' : '(?!)' })/\n/g;
  return \$copy;
}

sub buk {
  my( $p, $c ) = ( 0, 50e3 );
  my $copy = $main::string;
  1 while --$c and $p = index $copy, '!', $p;
  substr( $copy, 0, $p ) =~ tr[!][\n];
  return \$copy;
}
  

cmpthese ( -5, {
  cpp   => \&cpp,
  regex => \&regex,
  buk   => \&buk,
} );

__DATA__
__CPP__

#include <string>

long
  nth_index (
    const char* c_str_haystack,
    const char* c_str_needle,
    long n,
    long offset = 0
  ) {
    std::string haystack( c_str_haystack );
    std::string needle( c_str_needle );
    
    if( ! needle.size() || ! haystack.size() ) return -1;
    if( offset < 0 ) offset = 0;
    if( offset >= haystack.size() ) offset = haystack.size() - 1;
    size_t pos = haystack.find( needle, offset );
    while( --n ) {
      pos = haystack.find( needle, pos + 1 );
      if( pos == std::string::npos ) return -1;
    }
    return pos;
  }