Test2::Util - add _env_get() to wrap %ENV access.

A test might lock %ENV, so we should always check for key existence
before reading a key, or the lookup might trigger an exception. This
function wraps the check up and provides a default facility to make
logic that needs to consult %ENV more robust.

lib/Test2/Util.pm

@@ -36,13 +36,26 @@ our @EXPORT_OK = qw{
     try_sig_mask
 
     clone_io
+
+    _env_get
 };
 BEGIN { require Exporter; our @ISA = qw(Exporter) }
 
 BEGIN {
     *IS_WIN32 = ($^O eq 'MSWin32') ? sub() { 1 } : sub() { 0 };
 }
 
+# check for key existence before fetching from %ENV to avoid
+# locked hash issues. If it does not exist, or it does and the
+# value is undefined return $_[1] instead, thus allowing
+# a default value to be supplied if required.
+sub _env_get {
+    my ($key,$default) = @_;
+    my $got = exists($ENV{$key}) ? $ENV{$key} : undef;
+    $got = $default unless defined $got;
+    return $got;
+}
+
 sub _can_thread {
     return 0 unless $] >= 5.008001;
     return 0 unless $Config{'useithreads'};