Это функция языка C (может и в perl есть что-то аналогичное) - написать программку.
man p crypt
SYNOPSIS
#include <unistd.h>
char *crypt(const char *key, const char *salt);
DESCRIPTION
The crypt() function is a string encoding function. The algorithm is
implementation-defined.
The key argument points to a string to be encoded. The salt argument is
a string chosen from the set:
a b c d e f g h i j k l m n o p q r s t u v w x y z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
0 1 2 3 4 5 6 7 8 9 . /
....
The putpwent() function, used in the following example, is not part of
IEEE Std 1003.1-2001
#include <unistd.h>
#include <pwd.h>
#include <string.h>
#include <stdio.h>
...
int valid_change;
int pfd; /* Integer for file descriptor returned by open(). */
FILE *fpfd; /* File pointer for use in putpwent(). */
struct passwd *p;
char user[100];
char oldpasswd[100];
char newpasswd[100];
char savepasswd[100];
...
valid_change = 0;
while ((p = getpwent()) != NULL) {
/* Change entry if found. */
if (strcmp(p->pw_name, user) == 0) {
if (strcmp(p->pw_passwd, crypt(oldpasswd, p->pw_passwd)) == 0) {
strcpy(savepasswd, crypt(newpasswd, user));
p->pw_passwd = savepasswd;
valid_change = 1;
}
else {
fprintf(stderr, "Old password is not valid\n");
}
}
/* Put passwd entry into ptmp. */
putpwent(p, fpfd);
}