Does anyone know what $$ is meaning in perl?

[u24c02]

Does anyone know what $$ is meaning in perl?
Ans would you please let me know how I can get the input argument in perl?

 

[rancho_trojan]

$$ means the current process ID. You can find all pre-defined perl variables here https://perldoc.perl.org/perlvar.html or do a "man perlvar" and it should open the help page.