ERROR: Invalid psql argument: must be full path to a file named psql

Question

i try to monitor postgres 13 on windows 10 with the script check_postgres.pl of https://bucardo.org/downloads/check_postgres.pl.html#development.

I have this error

ERROR: Invalid argument: must be full path to a file nomed psql`

however, I did modify the variable $NO_PSQL_OPTION= 0 and I defined the path on the psql variable like this

$opt{PSQL}="C:\Program Files\PostgreSQL\13\bin"