#include <EXTERN.h>
#include <perl.h>

static PerlInterpreter *my_perl;

/** regex(string, operation)
**
** Used for =~ operations 
**
** Returns the number of successful matches, and
** modifies the input string if there were any.
**/

static int regex(SV **string, char *operation)
{
    int n;
    dSP;                            /* initialize stack pointer      */

    ENTER;                          /* everything created after here */
    SAVETMPS;                       /* ...is a temporary variable.   */

    PUSHMARK(sp);                   /* remember the stack pointer    */

    /* push a reference to the string onto the stack  */
    XPUSHs(newRV_noinc(*string)); 

    /* push the operation onto stack  */
    XPUSHs(sv_2mortal(newSVpv(operation,0))); 

    PUTBACK;                      /* make local stack pointer global */

    perl_call_pv("regex", G_ARRAY); /* call the function */

    SPAGAIN;                        /* refresh stack pointer         */
    n = POPi;       /* fetch the number of substiutions made */
    PUTBACK;

    FREETMPS;                       /* free that return value        */
    LEAVE;                         /* ...and the XPUSHed "mortal" args.*/

    return n;                     /* the number of substitutions made */
}

main (int argc, char **argv, char **env)
{
    char *embedding[] = { "", "regex.pl" };
    SV *text = newSV(0);
    int num_matches;

    if(argc < 2) {
	fprintf(stderr, "usage: regex <string>\n");
	exit(1);
    }

    sv_setpv(text, argv[1]);
    my_perl = perl_alloc();
    perl_construct( my_perl );
    perl_parse(my_perl, NULL, 2, embedding, NULL);
    perl_run(my_perl);
  
    if(num_matches = regex(&text, "m/([a-z]{4,6})/gi")) {
	AV *array;
	SV *match;
	int i;

	/* get a pointer to the @Matches array */
	array = perl_get_av("Matches", FALSE);

	/* take a look at each element of the @Matches array */
	for(i=0; i < num_matches; i++) {
	    match = av_shift(array); /* just like '$match = shift @Matches;' */
	    printf("%s ", SvPVX(match));
	}
	printf("\n\n");
    }
  
    /** Remove all vowels from text **/
    num_matches = regex(&text, "s/[aeiou]//gi");
    if (num_matches) {
	printf("regex: s/[aeiou]//gi...%d substitutions made.\n",
	       num_matches);
	printf("Now text is: %s\n\n", SvPVX(text));
    }

    /** Can we replace Perl with C?? **/
  
    if (!regex(&text, "s/Perl/C/")) {
	printf("Sorry, can't replace Perl with C\n\n");
    } 

    SvREFCNT_dec(text);
    perl_destruct_level = 0;
    perl_destruct(my_perl);
    perl_free(my_perl);
}