Its always a good idea to do basic status checking of even the most trivial system call. There's always a chance of failure on a live system. For example:

• incorrect path setup
• exhaustion of resources such as physical disk
• shell not available
• permissions or process limits
• missing utilities (although unlikely with sed)
• many others ....

system "sed 's/,)/)/' pbxiplp > pbxiplp1"
    and die "system call failed: $!";
[download]

See also system.