node ('somenode')
{
    stage ('checkout')
    {
        checkout([
            $class: 'PerforceScm', 
            credential: '111111111-1111-1111-1111-111111111111', //not actual value
            populate: [
                $class: 'ForceCleanImpl', 
                have: false,
                parallel: [
                    enable: false,
                    minbytes: '1024',
                    minfiles: '1', 
                    path: '/usr/local/bin/p4',
                    threads: '4'
                    ], 
                pin: '', 
                quiet: true
                ], 
            workspace: [
                $class: 'ManualWorkspaceImpl', 
                charset: 'none', 
                name: "jenkins-${NODE_NAME}-${JOB_NAME}", 
                pinHost: false, 
                spec: [
                    allwrite: false, 
                    clobber: false, 
                    compress: false, 
                    line: 'LOCAL', 
                    locked: false, 
                    modtime: false, 
                    rmdir: false, 
                    streamName: '', 
                    view: "//Depot/... //jenkins-${NODE_NAME}-${JOB_NAME}/..."
                    ]
                ]
            ]
        )
    }
    
    println "P4_CHANGELIST=${env.P4_CHANGELIST}"
    println "P4_CLIENT=${env.P4_CLIENT}"
    println "P4_PORT=${env.P4_PORT}"
    println "P4_USER=${env.P4_USER}"
    println "P4_TICKET=${env.P4_TICKET}"
    println "HUDSON_CHANGELOG_FILE=${env.HUDSON_CHANGELOG_FILE}"
    sh 'echo $P4_CHANGELIST'
}

...
P4 Task: syncing files at change: 1703
...
[Pipeline] }
[Pipeline] // stage
[Pipeline] echo
P4_CHANGELIST=null
[Pipeline] echo
P4_CLIENT=null
[Pipeline] echo
P4_PORT=null
[Pipeline] echo
P4_USER=null
[Pipeline] echo
P4_TICKET=null
[Pipeline] echo
HUDSON_CHANGELOG_FILE=null
[Pipeline] sh
[UI-CSR-Dev-tag test] Running shell script
+ echo

[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS