use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Terse=1;

sub foo {
   print "foo: bad args: ", Dumper \@_
      if @_ != 2 || $_[0] !~ /^[tf]/ || $_[1] !~ /statement/;

   my ($tf, $statement) = @_;

   if ($tf =~ /^t/) {  # Line 12
      print "true: $statement\n";
   } else {
      print "false: $statement\n"
   }
}

for my $statement ("the following statement is true",
                   "the preceding statement is false") {
   $statement =~ /\b(t|f|true|false)\b/ or next;
   foo($1, $statement);
}