Ah. Thanks for the sample. Also, thanks to Wind for narrowing the issue to the start_form/end_form because I was not able to replicate the problem before using <form>.

Anyway, here is my new solution:
I updated file name to $f to match original sample.

    if ($which_radio_button eq q{}) { 
      $query->delete("$f");
    }

[download]

see sample:

#!/usr/bin/perl -w

use CGI;
use strict;

my $query = CGI->new;
print $query->header;

my $button = $query->param('submit');
my @fs = ('test1.txt', 'test2.txt', 'test3.txt', 'test4.txt');

if ($button eq "save") {
  foreach my $f (@fs) {
    my $which_radio_button = $query->param("$f");
    print "for $f you selected $which_radio_button<BR>\n";
    if ($which_radio_button eq q{}) {
      $query->delete($f);
    }
  }
  #$query->delete_all();
}

print "<html><body>";
print $query->start_form();
#print $query->defaults('Restore to Defaults');
foreach my $f (@fs) {
  print  $query->radio_group(-name=>$f,
                                 -value=>['c','r','t','s'],
                                 -default=>'-');
  print "<BR>";   
}
print $query->defaults('Return to default');
print $query->submit(-name=>'submit',-value=>'save');
  
print $query->end_form();
print "</body></html>";

[download]

If you add $query->delete($f); where $f is empty you will achieve your desired result, as shown in the above example.

In reply to Re^3: How to get unselected radio_group() items after submitting form by wallisds
in thread How to get unselected radio_group() items after submitting form by slugger415

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