$ perl -Mstrict -Mwarnings -E '
use List::Util qw/reduce/;
say reduce { $a * $b } 1..6;
'            
Name "main::a" used only once: possible typo at -e line 3.
Name "main::b" used only once: possible typo at -e line 3.
720

##</code><code>##

$ perl -Mstrict -Mwarnings -E '
use List::Util qw/reduce/; $a || $b || 1;
say reduce { $a * $b } 1..6;
'
720

##</code><code>##

$ perl -Mstrict -Mwarnings -E '
use List::Util qw/reduce sum/; $a || $b || 1;
say reduce { $a * $b } 1..6;
say sum 1..6;
'
720
21