throw.
throw.

throw. causes execution to resume in the catcht. section of an explicit definition that invoked the current code, returning to immediate execution if there is no such catcht. .
 

For example:
main=: 3 : 0
 try. 
  sub y
 catcht.
  select. type_jthrow_
   case. 'aaaa' do. 'throw aaaa'  
   case. 'bbb'  do. 'throw bbb'   
   case. 'cc'   do. 'throw cc' 
   case.        do. throw.   NB. handled by a higher-level catcht. (if any)
  end.
 end.
)

sub=: 3 : 0
 if. y<0 do. type_jthrow_=: 'aaaa' throw. end.
 if. y<4 do. type_jthrow_=: 'bbb'  throw. end.
 if. y<8 do. type_jthrow_=: 'cc'   throw. end.
 (":y),' not thrown'
)

   main _4
throw aaaa
   main 1
throw bbb
   main 5
throw cc
   main 88
88 not thrown
A throw. can communicate information back to a catcht. through the use of a global name in a locale, as illustrated in the examples above.