How to split/extract substring before the first - from the right side of the string

[keshavgupta]

Spoiler

How to split/extract substring before the first - from the right side of the field on splunk search

For ex: My field hostname contains

Hostname = abc-xyz
Hostname = abc-01-def
Hostname = pqr-01

I want to see like below .

abc
abc-01
pqr

Please help me.

[ITWhisperer]

| rex "(?<host>[^\-]+)\-"