For completeness, and those interested in software archeology, you can use system and pipes in awk, here are some examples:

#Pipe output from print or printf
print | "sort"

#Pipe input through getline
"ls -l" | getline var

#Use the system() function call
system( "mkdir /home/fred" )
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But you wouldn't use this any more than you would drive to the shops in a chariot.