+# check that a PC protocol field is valid text
+sub is_pctext
+{
+ return undef unless length $_[0];
+ return undef if $_[0] =~ /[\x00-\x08\x0a-\x1f\x80-\x9f]/;
+ return 1;
+}
+
+# check that a PC prot flag is fairly valid (doesn't check the difference between 1/0 and */-)
+sub is_pcflag
+{
+ return $_[0] =~ /^[01\*\-]+$/;
+}
+
+# check that a thing is a frequency
+sub is_freq
+{
+ return $_[0] =~ /^\d+(?:\.\d+)?$/;
+}
+
+# check that a thing is just digits
+sub is_digits
+{
+ return $_[0] =~ /^[\d]+$/;
+}
+
+# does it look like a qra locator?
+sub is_qra
+{
+ return $_[0] =~ /^[A-Ra-r][A-Ra-r]\d\d[A-Xa-x][A-Xa-x]$/;
+}
+
+# does it look like a valid lat/long
+sub is_latlong
+{
+ return $_[0] =~ /^\s*\d{1,2}\s+\d{1,2}\s*[NnSs]\s+1?\d{1,2}\s+\d{1,2}\s*[EeWw]\s*$/;
+}
+
+# is it an ip address?
+sub is_ipaddr
+{
+ return $_[0] =~ /^\d+\.\d+\.\d+\.\d+$/ || $_[0] =~ /^[0-9a-f:]+$/;
+}
+
+# insert an item into a list if it isn't already there returns 1 if there 0 if not
+sub insertitem
+{
+ my $list = shift;
+ my $item = shift;
+
+ return 1 if grep {$_ eq $item } @$list;
+ push @$list, $item;
+ return 0;
+}
+
+# delete an item from a list if it is there returns no deleted
+sub deleteitem
+{
+ my $list = shift;
+ my $item = shift;
+ my $n = @$list;
+
+ @$list = grep {$_ ne $item } @$list;
+ return $n - @$list;
+}