~/git/StellarPGx: nextflow -v
nextflow version 18.10.1.5003
~/git/StellarPGx: singularity --version
singularity version 3.3.0-rc.1.658.g7427b73f1.dirty
~/git/StellarPGx: nextflow run main.nf -profile standard,test
N E X T F L O W ~ version 18.10.1
Launching `main.nf` [sleepy_visvesvaraya] - revision: ab68701493
ERROR ~ No such variable: ref_dir
-- Check script 'main.nf' at line: 350 or see '.nextflow.log' file for more details
Please can you help me understand this error