Check for definedness rather than truth. I don't usually run into this problem, but here's a solution I just made up on the spot. Caveat lector!

my      $MISC_FILE_DIR  = defined($_=shift) ? $_ : die usage(); 
my      $req            = defined($_=shift) ? $_ : die usage();
my      $inqfile        = defined($_=shift) ? $_ : die usage();
my      $sent           = defined($_=shift) ? $_ : die usage();
my      $status         = defined($_=shift) ? $_ : die "please specify
+ status\n" . usage();
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Another solution might be to use length to see if there's something other than an empty string there (undef evaluates to '' in a string context)

You could also lobby for the // operator to somehow make it into perl5. // is the "defined or" in perl 6 and would be used like this: my $MISC_FILE_DIR = shift // die usage();