The arrests in the Matthew Perry death case are shining a light on the sordid underbelly of the Hollywood drug scene … including a peek into one doctor’s darknet drug operations.

Dr. Mark Chavez, one of the two physicians charged in connection to Matthew’s death, used the dark web, cryptocurrencies and the United States Postal Service to sell illicit drugs … this according to a plea agreement obtained by TMZ.

A prior plea deal Chavez cut in March 2020 lays out the inner workings of a wide-reaching drug ring that provided buyers around the world with methamphetamine, MDMA and other controlled substances.

In the plea deal, Chavez copped to obtaining controlled substances from various sources of supply, and selling them on the darknet in exchange for crypto … namely, Bitcoin. He would then mail the drugs to buyers via USPS packages.

This was no small operation … when law enforcement raided Chavez’s home back in February 2020, agents say they found approximately 17,961 grams of a mixture and substance containing a detectable amount of meth in Chavez’s bedroom … that’s over 39 pounds!!!

Law enforcement says they also found two loaded firearms — a Glock .23 and a Luger pistol.

Chavez’s use of the USPS back in 2020 is also notable in terms of the Perry case … because, as we reported, the U.S. Postal Inspection Service helped investigate Matthew’s drug source.

Incredibly, despite this 2020 plea deal, Dr. Chavez was still able to practice medicine in California. In the Perry case, prosecutors claim he obtained ketamine by writing fraudulent prescriptions in a former patient’s name — then sold the ketamine to Dr. Salvador Plasencia, the other physician charged in the case.