This kind of works:

my @args=();
@args=("$pipeline/EXE/searchXY", "-5", "UEB2K005I", "locate", "234", "156", "4", "Print"); system(@args);

where earlier system "/usr/bin/mkfifo $pipeline/OUT/locate";

this sends it to the right place, but it gets the stuck at the process. Namely, the pipe is open for writing, and waits to be read, the C program gets paused until something reads the pipe... no problem so far :) This is as it should be from what I managed to understand about named pipes.

One more minor problem is that my whole script gets stuck at the point of when the pipe is open, waiting to be read... as the reading part is after the pipe open (the call to the C program opens it).

I suspect I need to start off the C program as some independent process, NOT use system(). I'll post the solutions when I fully work it out. The KEY here were named pipes :)

THANKS ALL :) The suggestions were RIGHT what I needed.