Happening to have a mod-perl enabled Apache 2 handy, I tried the following script:

#! x:/xampp/perl/bin/perl.exe
use strict;
use DBI;
use CGI qw/:standard/;
use Benchmark qw/timethese/;

my $dbh=DBI->connect("DBI:mysql:pandirecords",);
my $cgi = new CGI;
print $cgi->header;
print $cgi->start_html('DBI & mod-perl');
print '<pre>';
 
timethese( 10000, {
 
 inline => 'xinline',
 bind   => 'xbind',
});
print '</pre>';
print end_html;

sub xbind {
 my $parameter='0000284364';
 my $sql = 'SELECT insured_name FROM claims WHERE ref_underwriter = ?'
+;
 my $sth = $dbh->prepare( $sql );
 $sth->execute( $parameter );
 
 my @res = $sth->fetchrow_array;
}

sub xinline {
 my $parameter='0000284364';
 my $sql = 'SELECT insured_name FROM claims WHERE ref_underwriter ="' 
+. $parameter .'"';
 my $sth = $dbh->prepare( $sql );
 $sth->execute;
 
 my @res = $sth->fetchrow_array;
}
[download]

It had the following result:

cgi-bin
Benchmark: timing 10000 iterations of bind, inline...
      bind:  7 wallclock secs ( 2.56 usr +  0.65 sys =  3.21 CPU) @ 31
+12.36/s (n=10000)
    inline:  7 wallclock secs ( 2.60 usr +  0.50 sys =  3.11 CPU) @ 32
+20.61/s (n=10000)
[download]

and

mod-perl
Benchmark: timing 10000 iterations of bind, inline...
      bind:  7 wallclock secs ( 3.02 usr +  0.61 sys =  3.63 CPU) @ 27
+51.03/s (n=10000)
    inline:  8 wallclock secs ( 3.10 usr +  0.62 sys =  3.72 CPU) @ 26
+91.07/s (n=10000)
[download]

The results are a bit unexpected in that the mod-perl script seems to run a bit slower than the cgi-bin script. I guess this is due to the fact that both the browser, Apache and MySQL were running on the same machine and that the major part of the time was anyhow spent in fetching the records, rather than executing the perl-script.

Anyhow, I could not find any significant slowdown between the 'bind' and the 'inline' version of the script, so I must conclude that the huge difference you found must come from somewhere else.