Added expr parameter to monitor() for
executing arbitrary R expressions when files change, as an alternative
to running R scripts via the file parameter.
Added support for natural R syntax using curly braces
{} for multi-line expressions.
Added capture_output parameter to control whether
expression output is captured and displayed (default:
TRUE).
Added on_error parameter to control behavior when
expression execution fails ("continue" or
"stop").
Updated function documentation with comprehensive examples showing both string and language object expressions.
Updated README with detailed examples of expression execution features.
testthat for CRAN
compliance.