diff --git a/tools/grib_split b/tools/grib_split.pl
similarity index 92%
rename from tools/grib_split
rename to tools/grib_split.pl
index 1e86d8fda..492267ad7 100755
--- a/tools/grib_split
+++ b/tools/grib_split.pl
@@ -1,6 +1,11 @@
 #!/usr/bin/perl
 use strict;
 
+# ----------------------------------------------------------------------
+# Convert GRIB edition 2 multi-field (several fields per message) files
+# to single-field (one field per message)
+# ----------------------------------------------------------------------
+
 my $debug = 0;
 my $total = 0;
 my $previous_bitmap;