To prevent cut and paste, how about asking them to enter the id (or email address or whatever) first forward and then in reverse. Then reverse the second entry before comparing them for equality using a subroutine; for example:

# assuming the strings are now stored in $forward and $backward...
Reverse( \$backward );
unless ( $forward eq $backward ) {
    # code to handle confirm error
}

#...

# pass the string by reference e.g. Reverse( \$backward );
sub Reverse {
    my $sref = shift;
    my $reversed = '';
    for ( my $idx = length( $$sref ) - 1; $idx >= 0; $idx-- ) {
        $reversed .= substr( $$sref, $idx, 1 );
    }
    $$sref = $reversed;
}
[download]