@ARGV > 0 or die "Syntax: $0 <target dir> <filename> <md5sum> <mirror> [<mirror> ...]\n";
-my $md5cmd = `which md5sum`;
-$md5cmd or $md5cmd = `which md5`;
+sub which($) {
+ my $prog = shift;
+ my $res = `which $prog`;
+ $res or return undef;
+ $res =~ /^no / and return undef;
+ $res =~ /not found/ and return undef;
+ return $res;
+}
+
+my $md5cmd = which("md5sum");
+$md5cmd or $md5cmd = which("md5");
$md5cmd or die 'no md5 checksum program found, please install md5 or md5sum';
chomp $md5cmd;