or download this
D:\perl\psmail-1.0>perl -MData::Dumper -w -e "use strict; print Dumper
+({-font-family => 'not-valid'})"
Argument "family" isn't numeric in subtraction (-) at -e line 1.
...
my $q = 'CGI'->new;
print $q->Tr({-'font' - 'family', 'not-valid'});
-e syntax OK