tr: improve -d option

bin/tr

@@ -16,35 +16,45 @@ License: perl
 
 use strict;
 
+use File::Basename qw(basename);
+
+use constant EX_SUCCESS => 0;
+use constant EX_FAILURE => 1;
+
+my $Program = basename($0);
+
 my(
     %opt,           # option hash
     $string1,	    # from set
     $string2,       # to set
 );
 
-
-END {
-    close STDOUT || die "$0: can't close stdout: $!\n";
-    $? = 1 if $? == 255;  # from die
-}
-
 sub usage {
-    warn "$0: @_\n" if @_;
-    die "usage: $0 [-csd] string1 string2 [file ...]\n";
+    warn "usage: $Program [-cdsUC] string1 string2\n";
+    exit EX_FAILURE;
 }
 
 @opt{ qw/c s d U C/ } = ('') x 5;
 
-while ($ARGV[0] =~ s/^-(?=.)//) {
+while (defined($ARGV[0]) && $ARGV[0] =~ s/^-(?=.)//) {
     for my $flag (split(//,$ARGV[0])) {
-        usage("unknown flag: `$flag'") unless 'csdUC' =~ /\Q$flag/;
-        warn "$0: `$flag' flag already set\n" if $opt{$flag};
+        if ('cdsUC' !~ m/\Q$flag/) {
+            warn "unknown option: '$flag'\n";
+            usage();
+        }
         $opt{$flag} = $flag;
     }
     shift;
 }
-
-usage("Not enough arguments") unless @ARGV > 1;
+my $narg = ($opt{'d'} && !$opt{'s'}) ? 1 : 2;
+if (scalar(@ARGV) < $narg) {
+    warn "missing operand\n";
+    usage();
+}
+if (scalar(@ARGV) > $narg) {
+    warn "extra operand\n";
+    usage();
+}
 
 # remove spurious [...]
 for (($string1, $string2) = splice(@ARGV, 0, 2)) {
@@ -60,11 +70,12 @@ eval qq{
 	tr[$string1][$string2]$opts;
 	print;
     }
+    1;
+} or do {
+    warn "$Program: $@\n";
+    exit EX_FAILURE;
 };
-
-die if $@;
-
-exit (0); # XXX: Doen't detect failed opens
+exit EX_SUCCESS; # XXX: Doen't detect failed opens
 
 __END__
 
@@ -88,23 +99,23 @@ Here are the options:
 
 =over
 
-=item c
+=item -c
 
 Complement the SEARCHLIST.
 
-=item d
+=item -d
 
 Delete found but unreplaced characters.
 
-=item s
+=item -s
 
 Squash duplicate replaced characters.
 
-=item U
+=item -U
 
 Translate to/from UTF-8.
 
-=item C
+=item -C
 
 Translate to/from 8-bit char (octet).