diff --git a/rpn b/rpn
index 268cc8f..d366bfd 100755
--- a/rpn
+++ b/rpn
@@ -3,14 +3,16 @@ use warnings;
 use strict;
 use Term::ANSIColor;
 use Math::Trig ':pi';
+use Scalar::Util qw(looks_like_number);
 
 my @stack;
 my $input_color = 'red';
 my $stack_color = 'blue';
+my $format;
 print color $input_color;
 while (<>) {
     for (split) {
-	if (m{^[-+*/%]|\*\*$}) {
+	if (m{^([-+*/%]|\*\*)$}) {
 	    my $y = pop @stack;
 	    my $x = pop @stack;
 	    my $z = eval "$x $_ $y";
@@ -41,13 +43,20 @@ while (<>) {
 	} elsif (m{^ld$}) {
 	    my $x = pop @stack;
 	    push @stack, log($x) / log(2);
+	} elsif (m{^format$}) {
+	    $format = pop @stack;
 	} else {
 	    push @stack, $_;
 	}
     }
     for (@stack) {
 	print color $stack_color;
-	print "$_\n";
+	if ($format && looks_like_number($_)) {
+	    printf($format, $_);
+	    print "\n";
+	} else {
+	    print "$_\n";
+	}
     }
     print color $input_color;
 }