A drug addict who dragged an 82-year-old man to the ground during an attempted robbery in Perth, causing the victim to fall backwards and hit his head on the pavement, has been jailed for 39 months.

Heavy methamphetamine user Cody George Ugle, 23, tried to pull a gold necklace off the elderly man's neck as he walked through a shopping centre car park in Victoria Park in January.

Ugle committed the offence while on bail for robbing a woman of her mobile phone as she stood at a bus stop in East Victoria Park in December.

It also breached a nine-month suspended imprisonment order that a court had imposed on him for another crime.

The District Court of WA heard Ugle had a deprived upbringing and his life was "spiralling out of control" as he lived in an abandoned house and looked for people to rob to feed his intravenous drug habit.

"Then he picks on an elderly target - what a coward," Judge Simon Stone said on Tuesday.

"Callously, you left him on the ground bleeding."

Ugle will be eligible for parole after serving half of his term.