The basic operations on customization variables are to set and retrieve their values.
The customization variables also valid in the main program out of the HTML converter are handled differently if their associated values are strings or arrays. Conversely, customization variables only relevant for the conversion phase set in the main program are always set by associating a string, an array reference or a hash references to customization variables in the same way.
This section describes customization variables set in the main program. These variables are in general passed to converters. It is also possible to set customization variables in the converters only, not in the main program. This is explained later on (see Setting and Getting Conversion Customization Variables).