This is actually a good question, because some other people might ask this too in the future. I've actually written some similar code recently, so I'll try to make a standalone example from it.

The following is a form with a single repeatable text input field. It works better in some browsers, but the form is still usable from any browser (even without javascript or css).

You can currently view this example live at http://russell2.math.bme.hu/~ambrus/pu/cpdemo/cpdemo.cgi.

Below is the executable code of the CGI, which you should call cpdemo.cgi. 

#!/usr/local/bin/perl -T
# Standalone demo for repeatable html input field.

use warnings; use strict;

use CGI;

sub escapeHTML {
    my($v) = @_;
    $v =~ s/&/&/g;
    $v =~ s/</&lt;/g;
    $v =~ s/>/&gt;/g;
    $v =~ s/"/&quot;/g;
    $v;
}

our(@nam);

our $ownurl = "cpdemo.cgi";

sub hparm {

    @nam = grep { length } CGI::param("fld-nam");

}

sub htop {

    print
        qq{Content-Type: text/html; charset=utf-8\n},
        qq{\n},
        qq{<!doctype html public "-//W3C//DTD HTML 4.01//EN" "http://w
+ww.w3.org/TR/html4/strict.dtd">\n},
        qq{<html>\n},
        q{
        <head>
        <meta http-equiv="content-type" content="text/html; charset=ut
+f-8">
        <title>Repeatable html input field demo</title>
        <link rel="stylesheet" href="cpdemo.css" type="text/css">
        <link id="style_js" rel="alternate stylesheet" disabled href="
+cpdemojs.css" type="text/css" title="style_js">
        <script type="text/javascript" src="cpdemo.js"></script>
        </head>
        <body>
        <h1>
        Repeatable html input field demo
        </h1>
    };
    # note: do not add a title attribute to the first style sheet but 
+do not delete the one from the second stylesheet or this breaks in ko
+nqueror

}

sub hform {

    print q{
        <p><a href="} . $ownurl . q{">Clear form</a>
        <form action="} . $ownurl . q{" method="POST" accept-charset="
+utf-8">
    };

    my $nrepeat = CGI::param("rep-nam");
    $nrepeat = $nrepeat ? int($nrepeat) : 1;
    defined(CGI::param("add-nam")) and $nrepeat++;
    $nrepeat < @nam and $nrepeat = @nam;
    1 <= $nrepeat or $nrepeat = 1;
    $nrepeat <= 1022 or $nrepeat = 1022;
        
    my @val = @nam;
    for my $krepeat (0 .. $nrepeat + 0) {
        print qq{
            <div
        };
        if ($nrepeat == $krepeat) {
            print qq{ class="form_addtemplate" id="addtpl-nam"};
        }
        print qq{
            >
            <p>Name: 
            <input type="text" name="fld-nam" size="60" 
                value="}, escapeHTML(@val ? shift @val : ""), qq{">
                <span class="form_tailloc">
        };
        if ($nrepeat - 1 == $krepeat) {
            print qq{
                <span class="form_tail" id="tail-nam">
                <a class="form_addlink" href="javascript:void\(addanot
+her\(&quot;nam&quot;\)\)">Add another</a>
                </span>
            };
        }
        print q{</span>};
        if ($nrepeat == $krepeat) {
            print qq{
                <small class="form_addusage"> 
                (Too add one more such field, fill all of them and pre
+ss preview.)
                </small>
            };
        }
        print q{</div>}; # addtpl
    }
    print 
        q{<input type=hidden name="rep-nam" value="} . $nrepeat . qq{"
+>\n};
        
    print qq{
        <p>
        <input name="preview" type="submit" value="Preview" class="for
+m_submitbutton">
        </form>
    };

}

sub hout {

    print q{<p><textarea class="out_curtext" rows="8" cols="70">};
    for my $val (@nam) {
        print escapeHTML($val) . "\n";
    }
    print qq{</textarea>\n};

}

sub hbot {

    print qq{</body></html>\n};

}

sub hmain {
    ${^TAINT} or die "run in taint mode (perl -T) please";
    hparm;
    htop;
    hform;
    hout;
    hbot;
}

hmain;             

1;

__END__

[download]

It needs three more files for support. The first one is cpdemo.js 

/*
Standalone demo for repeatable html input field: javascript.
*/


function addanother(fld) {

    // vvv first part should work in any browser
    var tpl = document.getElementById("addtpl-" + fld);
    var cpy = tpl.cloneNode(true);
    cpy.id = "";
    cpy.className = "";
    tpl.parentNode.insertBefore(cpy, tpl);

    // vvv second part only works in some browsers, but the form still
+ works without it
    var tlo = cpy.getElementsByClassName && cpy.getElementsByClassName
+("form_tailloc")[0];
    var tco = document.getElementById("tail-" + fld);
    if (tlo && tco)
        tlo.appendChild(tco);

};

function initcpdemo() {
    var ssa = document.getElementById("style_js");
    ssa.disabled = false;
};

initcpdemo();


/* END */

[download]

The second is cpdemo.css 

/*
Standalone demo for repeatable html input field: common css.
*/

.form_addlink {
    display: none;
}

/* END */

[download]

And the third one is cpdemojs.css. 

/*
Standalone demo for repeatable html input field: css used if javascrip
+t is available.
*/

.form_addtemplate, .form_addusage {
    display: none;
}
a.form_addlink { 
    display: inline;
}

/* END */

[download]

Update: added missing right angle bracket for the div tag (thanks, W3C HTML validator).

In reply to Re: replicating blocks of code in perl and cgi by ambrus
in thread replicating blocks of code in perl and cgi by gogoglou

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