$ grep /dev/urandom **/*.c
util.c:4550:#  define PERL_RANDOM_DEVICE "/dev/urandom"

##</code><code>##

/* This test is an escape hatch, this symbol isn't set by Configure. */
#ifndef PERL_NO_DEV_RANDOM
#ifndef PERL_RANDOM_DEVICE
   /* /dev/random isn't used by default because reads from it will block
    * if there isn't enough entropy available.  You can compile with
    * PERL_RANDOM_DEVICE to it if you'd prefer Perl to block until there
    * is enough real entropy to fill the seed. */
#  define PERL_RANDOM_DEVICE "/dev/urandom"
#endif
    fd = PerlLIO_open(PERL_RANDOM_DEVICE, 0);
    if (fd != -1) {
    	if (PerlLIO_read(fd, (void*)&u, sizeof u) != sizeof u)
	    u = 0;
	PerlLIO_close(fd);
	if (u)
	    return u;
    }
#endif