You might want to scan down the man page for the perl debugger ("perldoc perldebug") to the section about "The Perl Profiler". If you put each of your system calls into its own little perl subroutine, then run the script as follows:

 perl -d:DProf  your_script.pl
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the script will do what it normally does, and while it's doing that, the perl interpreter will be saving tons of trace and timing information to a file in your current directory. After the run is over, you can get a summary that profiles the time spent in each subroutine (i.e. running each system call) by running this utility that comes as part of the Perl distribution:

 dprofpp tmon.out
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(where "tmon.out" is the name that the debugger's profiling module assigns to the trace file that it creates, as explained in the perldebug man page).