My html webpage calls php script to upload files to the server from a local computer as follows. <form enctype="multipart/form-data" action="upload.php" method="POST"> <p><b><h3> <font color="#003366"> (1) Upload your reading text file. </font> </h3> </b> </p> <INPUT type="file" name="uploaded" size="50" > <br/> <input type="submit" name="files" value="upload"> </form> In order to process with an uploaded file, my php script calls shell script $output=system('/bin/sh connector_0.sh'); and my shell script is composed of a series of python/perl scripts. #!/bin/sh python main_senselearner_final_0.py senseLearner.pl -i Uploaded_Files/slinput_0.txt -o Uploaded_Files/presloutput_0 .txt -model modelNNCollocations -model modelJJCollocations -model modelVBColloc ations -pos python smutngslout_0.py python genhtml_0.py Now, the problem is the following: all python scripts in shell script worked fine through php. But perl script didn't work. When I run shell script by myself in my server, all four scripts in shell worked perfectly. However, when I run shell script from php, only perl script doesn't work. Would you please give me any tips to solve this problem? Many thanks!!!