perl -e "my $foo; my $bar = 3; $bar += $foo; print $bar"
versus
perl  -Mwarnings -e "my $foo; my $bar = 3; $bar += $foo; print $bar"

##</code><code>##

# ++ is a short cut for $foo = $foo + 1
perl  -Mwarnings -e "my $foo; $foo++; print $foo"