use Encode;

# ... assign goofy string value to $test ...

$test =~ s/%([0-9A-F]{2})/chr(hex($1))/eg; # convert hex digits to oct
+ets

$test = decode( "utf8", $test );  # convert octets to unicode characte
+rs
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The "decode" call (provided the Encode module) might not be necessary, depending on what you need to do with the string value. If you're just going to print it to a "raw" file handle, just print it with no further ado. But to use it as utf8 text (or print to a file handle that has been set to use utf8 mode) you need to "decode" it first.

UPDATE: Of course, ikegami's approach is the better way to go.