Your question is a bit confusing as you cannot do a numeric operation on a string like "20 ducks in a row" when warnings and use strict are in force

No - you *can* do the numeric operation on that string if warnings and strict are enabled, and it gives the same result as you get without strict and warnings ... except, of course, that you additionally get a warning:

C:\>perl -Mstrict -Mwarnings -e "my $x = '20 ducks in a row'; $x += 17
+;print $x"
Argument "20 ducks in a row" isn't numeric in addition (+) at -e line 
+1.
37
C:\>
[download]

Cheers,
Rob