Has the behavior of 'run script' changed in Snow Leopard?

Question

These work fine:
tell application "Safari"
return URL of front document
end tell
tell application "Safari"
set longURL to URL of front document
return longURL
end tell
This does not:
set getFrontmostURLCommand to "URL of front document"
tell application "Safari"
set longURL to run script getFrontmostURLCommand
end tell
return longURL
Why? It looks like a script interpretation error but I can't figure out what's wrong.
The error returned is:
error "Safari got an error: Can’t get URL of document 1." number -1728 from "URL of front document"

Answer 1

I see. Is there a way to make the application variable? I'm writing a function because getFrontmostURLCommand works with a couple of different browsers and I want it to be run conditionally based on the user's browser. Something like this:
set defaultBrowser to GetDefaultWebBrowser()
on GetDefaultWebBrowser()
set _scpt to "export VERSIONERPERL_PREFER_32BIT=yes; " & -
"perl -MMac::InternetConfig -le " & -
"'print +(GetICHelper \"http\")[1]'"
return do shell script _scpt
end GetDefaultWebBrowser
on defaultGetFrontmostURLCommand(defaultBrowserApplication)
tell application defaultBrowserApplication to set longURL to URL of front document
end defaultGetFrontmostURLCommand
on caminoGetFrontmostURLCommand()
tell application "Camino" to set longURL to URL of current tab of browser window 1
end caminoGetFrontmostURLCommand
if defaultBrowser is in {"Safari", "WebKit", "Opera"} then
defaultGetFrontmostURLCommand(defaultBrowser)
else if defaultBrowser is "Camino" then
caminoGetFrontmostURLCommand()
end if
set the clipboard to longURL