# this is pseudo-code
$filename = '>test' or '+test'
open(HANDLE, ">$filename");   # >>test or >+test (ruh-roh!)

# likewise
$filename = 'ls|' or '>test;
open(HANDLE, "$filename");    # ls| (pipe) or clobbers 'test'

# generally safe (in that behavior is not unexpected):
open(PIPE, " $command |")
open(PIPE, "| $command\0");   # safe version of "|ls"
open(FILE, "> $filename\0");  #                 ">file"
open(FILE, " $filename\0");   #                 "file"