You already got suggestions on how to fix these errors:

Variable "$CONFIG" is not imported at ./Chapter9_Exer3 line 15.
Variable "$OUTPUT" is not imported at ./Chapter9_Exer3 line 20.
Global symbol "$CONFIG" requires explicit package name at ./Chapter9_E
+xer3 line 15.
Global symbol "$OUTPUT" requires explicit package name at ./Chapter9_E
+xer3 line 20.
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You open the filehandles CONFIG and OUTPUT, and then try to use the variables $CONFIG and $OUTPUT, these are two different things. You need to either change your open calls to use lexical variables, like I showed here, or remove the $ sigil, as pointed out by Your Mother and kcott.

syntax error at ./Chapter9_Exer3 line 8, near "'three_Freds.out':"
Can't use global $0 in "my" at ./Chapter9_Exer3 line 12, near "Usage: 
+$0"
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The first error was pointed out by poj: You have a typo in that line. The second error is just being caused by the parser getting confused after seeing the first error.