Calling AppleScript handler from tell block - applescript

Question

I'm trying to call a function/handler from a tell block, but AppleScript keeps throwing an error:
Result: error "AppleEvent handler failed." number -10000
The script fails where I'm calling start_varnish():
tell application "System Events"
set iTermIsRunning to exists (processes where name is "iTerm")
end tell
tell application "iTerm"
activate
try
tell current terminal
if iTermIsRunning then
launch session "Default Session"
end if
tell the last session
my start_varnish()
end tell
end tell
on error err
log "Reopening iTerm2"
reopen
tell current terminal
tell the last session
my start_varnish()
end tell
end tell
end try
end tell
on start_varnish()
set name to "Varnish Cache"
end start_varnish
When I move the contents of the handler and place it directly in the code above, it works fine, but I would like to wrap the functionality in a handler for reusability.

Answer 1

The closest fix I could find looks as follows:
tell application "System Events"
set iTermIsRunning to exists (processes where name is "iTerm")
end tell
tell application "iTerm"
activate
try
tell current terminal
if iTermIsRunning then
launch session "Default Session"
end if
my start_varnish()
end tell
on error err
log "Reopening iTerm2"
reopen
my start_varnish()
end try
end tell
on start_varnish()
tell application "iTerm"
tell current terminal
tell the last session
set name to "Varnish Cache"
end tell
end tell
end tell
end start_varnish
I'm not sure if the scoping in my original question for cell current terminal and tell the last session is understood inside the context of the start_varnish() handler.