if -> 'if' test '{' block_contents '}'
      [ 'elseif' test '{' block_contents '}' ]*
      [ 'else' '{' block_contents '}' ]

test -> boolean_XPath_expression

block_contents -> [ command | if | foreach ]*

The test tests found after if, elseif, ..., elseif are evaluated in turn until a test evaluates as true(). When this happens, the evaluation of tests stops there and the block_contents following the successful test is run. If no test evaluates as true(), then the block_contents following else, if any, is run.

Examples:

if $table-container and count($table-container//td) = 1 {
    replace(copy(.), $table-container);
}

if ./node() {
    unwrap-element();
} else {
    delete();
}

if @href {
    remove-attribute("name");
} elseif ./node() {
    unwrap-element();
} else {
    delete();
}