Perhaps you should just try it?

> { echo out; echo err >&2; } >f1 2>&1
> cat f1
out
err
> { echo out; echo err >&2; } 2>&1 >f1
err
> cat f1
out
[download]

Redirection order definitely DOES matter in the shell. (Hmm, unless it's shell-specific? I'm using bash)

And just to do exactly what you said..

> perl -e'print "print\n"; warn "warn"' >f1 2>&1
> cat f1
warn at -e line 1.
print
> perl -e'print "print\n"; warn "warn"' 2>&1 >f1
warn at -e line 1.
> cat f1
print
[download]

In the first case both print and warn go to the file, in the second case warn goes to stdout and print to the file.