It's a cautionary cleanup in case you're passing garbage as parameters.

Perhaps you should use Scalar::Util::looks_like_number to confirm a numerical value.

I think you missed the "d" there :)

There is no letter 'd' in the line:

    my $seconds = sprintf( "%02.3f", ( ( $sectime - ( $hours * 3600 ) 
+) - ( $minutes * 60 )) );
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Update

Why not just:
 my ( $hours, $minutes, $seconds ) = split /:/, $time;
Because I want that if you pass only one value, it defaults to seconds, and to minutes:seconds with only two values.

Then try it like this:

my ( $hours, $minutes, $seconds ) = ( split /:/, $time )[ -3, -2, -1 ]
+;
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