The study investigated the learner perceptions of a CALL component in a blended language learning context. 52 Taiwanese college students attended instructional classroom sessions and did weekly online assignments in the form of interactive web-based exercises over one semester. Their learning performance was measured by means of two computer-based language assessments at the mid-point and final part of the semester. Learners' perceptions of the interactive web-based exercises were elicited by a computerized survey conducted at the end of the semester. The results reported on the survey revealed that participants perceived the interactive web-based exercises as interesting but only modestly so. This was probably attributable to the difficulty level of the created exercises and a lack of diverse exercise formats. Even so, having easy access, receiving immediate feedback, allowing multiple attempts, and enabling self-paced learning were mentioned as benefits of the constructed exercises. More importantly, most participants reported the effectiveness of these exercises in improving their reading comprehension and vocabulary leaning. This confirmed language assessment results that demonstrated significant gains in reading comprehension and vocabulary knowledge. Implications include suggestions for language teachers and program developers for improving the way web-based learning activities are created and implemented.