$ perl -le 'use warnings qw(FATAL); my $a = "2:" + 3; print $a'
5

##</code><code>##

$ perl -le 'use warnings; my $a = "2:" + 3; print $a'
Argument "2:" isn't numeric in addition (+) at -e line 1.
5

##</code><code>##

$ perl -le 'use warnings qw(FATAL all); my $a = "2:" + 3; print $a'
Argument "2:" isn't numeric in addition (+) at -e line 1.