foreach $thing (keys(%INPUT)) {
        if(ref($INPUT{$thing}) eq "ARRAY") { $INPUT{$thing} = join('^', $$INPUT{$thing}); }
#       if($#INPUT{$thing}) { $INPUT{$thing} = join('^', $$INPUT{$thing}); }
}

##</code><code>##

foreach $thing ( keys %INPUT ) 
{
    if( ref( $INPUT{$thing} ) eq "ARRAY" ) 
    { 
        $INPUT{$thing} = join '^', @{$INPUT{$thing}}
    }
}

# You can also write the above like this:
$INPUT{$_} = join '^', @{$INPUT{$_}} for grep {"ARRAY" eq ref $INPUT{$_}} keys %INPUT