The worst-case similar scenario I have encountered is where 0, '', undef(), "NULL", "null", "N/A" and "NA" all had to evaluate false and just about everything else as true. Commenting out my extra NA requirement would produce something like:

if ( True( $value ) ) {
}
else {
}

sub True {
    defined $_[0]
      and $_[0]
      and ( uc( $_[0] ) ne "NULL" )
      # and $_[0] !~ /^N\/?A$/
      ;
}
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