This looks like a CGI. The technique of building up an error string and reporting it if present may be of use:

my $errstr = '';

for my $param( qw( name email phone url requests ) ) {
    $errstr .= "Please enter your $param<br>\n" unless defined param($
+param);
}

# if $errstr is true we have some errors, so tell user
if ( $errstr ) {
    print "Content-Type: text/html\n\n";
    print "<p>Please click back and correct these error(s):\n<p>" . $e
+rrstr;
  exit 0;
}

# got data OK so continue processing
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