Integrate perl with the other meson builds

One big dev shell!

src/perl/lib/Nix/Utils.pm

@@ -0,0 +1,47 @@
+package Nix::Utils;
+
+use utf8;
+use File::Temp qw(tempdir);
+
+our @ISA = qw(Exporter);
+our @EXPORT = qw(checkURL uniq writeFile readFile mkTempDir);
+
+$urlRE = "(?: [a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~\*]+ )";
+
+sub checkURL {
+    my ($url) = @_;
+    die "invalid URL '$url'\n" unless $url =~ /^ $urlRE $ /x;
+}
+
+sub uniq {
+    my %seen;
+    my @res;
+    foreach my $name (@_) {
+        next if $seen{$name};
+        $seen{$name} = 1;
+        push @res, $name;
+    }
+    return @res;
+}
+
+sub writeFile {
+    my ($fn, $s) = @_;
+    open TMP, ">$fn" or die "cannot create file '$fn': $!";
+    print TMP "$s" or die;
+    close TMP or die;
+}
+
+sub readFile {
+    local $/ = undef;
+    my ($fn) = @_;
+    open TMP, "<$fn" or die "cannot open file '$fn': $!";
+    my $s = <TMP>;
+    close TMP or die;
+    return $s;
+}
+
+sub mkTempDir {
+    my ($name) = @_;
+    return tempdir("$name.XXXXXX", CLEANUP => 1, DIR => $ENV{"TMPDIR"} // $ENV{"XDG_RUNTIME_DIR"} // "/tmp")
+        || die "cannot create a temporary directory";
+}