txt2pre: eliminate 'Use of uninitialized value ...' warnings

the 404 pages don't have $url

diff --git a/txt2pre b/txt2pre
index 31fdb78..5bf8811 100644 (file)
--- a/txt2pre
+++ b/txt2pre
@@ -1,5 +1,5 @@
 #!/usr/bin/env perl
-# txt2pre --- convert my site's txt files to `pre'-based html
+# txt2pre --- convert my site's txt files to `pre'-based atom/rss/html
 
 # Copyright (C) 2014-2021 all contributors <meta@public-inbox.org>
 # Copyright (c) 2021 Amin Bandali <bandali@gnu.org>
@@ -211,10 +211,10 @@ $txt = linkify(html_esc($txt));
 my $upd_iso8601 = `date -Iseconds -ud '$upd' | tr -d \\\\n` if $upd;
 my $pub_iso8601 = `date -Iseconds -ud '$pub' | tr -d \\\\n` if $pub;
 my $pub_rfc5322 = `date -uRd '$pub' | tr -d \\\\n` if $pub;
-my $url_html = $url =~ s/(?:[.]$lang)?[.]txt$/.html/r;
-$url_html =~ s|/bandali-(.*)|/$1|;
-my $slug = $url_html =~ s|.*/(.*)[.]html$|$1|r;
-my $note_id = "$feed_id:$slug";
+my $url_html = $url =~ s/(?:[.]$lang)?[.]txt$/.html/r if $url;
+$url_html =~ s|/bandali-(.*)|/$1| if $url_html;
+my $slug = $url_html =~ s|.*/(.*)[.]html$|$1|r if $url_html;
+my $note_id = "$feed_id:$slug" if $url_html;
 
 # note header
 if ($format eq 'html') {