Tag Type C++ code (built in to libHForm/scan_ifs.cc)
Attributes var=varname The variable whos value must be "1" or "on" to cause the block of text and other tags up to a matching {Else} or {/If} to be displayed.
value= If present, check to see if varname is equal to a particular value instead of boolean true/false.
not If present, reverses the result of the comparison.
Contained Tags May contain a matching Else, or even a nested If tag. Also can contain any typical Body tags
Related Tags None.

The following code displays a special help message only if the checkbox/boolean "needhelp" is checked/true. Only one of the messages will be displayed. Note that other RPM tags or HTML tags could have been embedded within the {If} ... You can even nest other If's and RPM will do the right thing.
  . . .

  {If var=neephelp}
    Man, you really need help!
    I'm glad you're getting the hang of it.

  . . .