print "PS file doesn't exist!" unless -e $image_output . ".ps"; #### The status returned by the last pipe close, backtick (``) command, or system() operator. Note that this is the status word returned by the wait() system call (or else is made up to look like it). Thus, the exit value of the subprocess is actually ($? >> 8), and $? & 255 gives which signal, if any, the process died from, and whether there was a core dump. (Mnemonic: similar to sh and ksh.)