You would pass in the arguments using the format:
{DEBUG 1}
{MINAGE 18}
{MAXAGE 65}
Then, in the code you would do something like:
#Set default arguments in case you forget to pass args
set uargs {}
set debug 0
set minage 0
set maxage 100
#Get the user arguments from args
keylget args ARGS uargs
#Get each individual key/value pair argument from uargs
catch {keylget uargs DEBUG debug} ;#Overrides the default if supplied
catch {keylget uargs MINAGE minage} ;#Overrides the default if supplied
catch {keylget uargs MAXAGE maxage} ;#Overrides the default if supplied
Hope that helps :D.
-Brian Hochenedel