bin2dec

#!/usr/bin/perl -w

use strict;

$0=~ /([^\/]+)$/s or die "?";
my $myname=$1;
sub usage {
	print "$myname 101001010
  Convert binary values to decimals.
  (Well, it uses perl's builtin decimals so it's not unlimited precision:/)
";
exit @_;
}

my @values;
for (my $i=0; $i<=$#ARGV; $i++) {
	local $_=$ARGV[$i];
	if (/^--?h(elp)?$/) {
		usage
	} elsif ($_ eq '--') {
		push @values, @ARGV[$i+1..$#ARGV];
		last;
	} elsif (/^-/) {
		warn "Unknown option '$_'\n";
		usage(1)
	} else {
		push @values, $_
	}
}
usage unless @values;

my $res=0;
number: for (@values) {
	my $t=0;
	my $w=1;
	for (my $i=length($_)-1; $i>=0; $i--) {
		if (substr($_,$i,1) eq '1') {
			$t+= $w;
		} elsif (substr($_,$i,1) ne '0') {
			warn "String '$_' is not a binary number, ignoring.\n";
			$res=1;
			next number;
		}
		$w*=2;
	}
	print $t."\n";
}
exit($res);