sub foo {}

#foo(substr "hello", 10, 1);       # fatal error as you pointed out
#foo(+substr "hello", 10, 1);      # I thought this would be a workaround
foo(scalar substr "hello", 10, 1); # but you need something like this

print "This only gets printed if the last line didn't cause a fatal error\n";

##</code><code>##

perl -e '+$a = "Hello, world!\n"; print $a'
Hello, world!