diff --git a/perl/lib/Nix/Utils.pm b/perl/lib/Nix/Utils.pm
new file mode 100644
index 0000000000..943b8dd4ab
--- /dev/null
+++ b/perl/lib/Nix/Utils.pm
@@ -0,0 +1,8 @@
+package Nix::Utils;
+
+$urlRE = "(?: [a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~\*]+ )";
+
+sub checkURL {
+    my ($url) = @_;
+    die "invalid URL ‘$url’\n" unless $url =~ /^ $urlRE $ /x;
+}