$re = '/\R(?!Module Statements,)/m';
$str = 'Module Statements,Module,Collection of primitive building blocks and instances of other modules that comprise a network and or instrument. Two types handoff or internal,A redefinition of a module_def shall overwrite a previously defined module_def having the same module_name within the same nameSpace_name.,6.4.5.a),
Module Statements,,,A module_def shall have at least one port_def unless it is the top module and contains an AccessLink statement,6.4.5.b),
Module Statements,,,"The following objects shall have unique names within a module_def:
port_name
? scanRegister_name
? dataRegister_name
? one_hot_scan_group_name
? scanMux_name
? dataMux_name
? clockMux_name
? one_hot_data_group_name
? logicSignal_name
? alias_name",6.4.5.c),
Module Statements,,,"The following objects shall have unique names within a module_def:
instance_name
? scanInterface_name",6.4.5.d),
Module Statements,,,"An inputPort_name shall be one of the following
scanInPort_name
? shiftEnPort_name
? captureEnPort_name
? updateEnPort_name
? dataInPort_name
? selectPort_name
? resetPort_name
? tmsPort_name
? tckPort_name
? clockPort_name
? trstPort_name
? addressPort_name
? writeEnPort_name
? readEnPort_name
",6.4.5.e),
Module Statements,,,"An outputPort_name shall be one of the following:
? scanOutPort_name
? dataOutPort_name
? toShiftEnPort_name
? toUpdateEnPort_name
? toCaptureEnPort_name
? toSelectPort_name
? toResetPort_name
? toTckPort_name
? toTmsPort_name
? toClockPort_name
? toTrstPort_name
? toIRSelectPort_name",6.4.5.f),
Module Statements,,,Multiple inputPort_name port functions that are of type vector_id may share the same SCALAR_ID as long as the indexes form a contiguous range and every index range is of the same either ascending or descending type.,6.4.5.g),
Module Statements,,,Multiple outputPort_name port functions that are of type vector_id may share the same SCALAR_ID as long as the indexes form a contiguous range and every index range is of the same either ascending or descending type.,6.4.5.h),';
$subst = " ";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php