Custom Lasso tag to check existence of a GET/POST parameter in Lasso script

[elizas]

This is a custom lasso tag which takes the name of HTTP-POST or GET parameter (submitted through form-posting for example) as argument and returns a Boolean value to indicate whether that parameter is found. It returns true if a parameter with that name is found in the set of HTTP POST/GET parameters and false if the parameter is not found.

This Lasso custom tag is like isset() function in PHP.

Any suggestions are welcomed.