How to unencode a string

[jakecjacobson]

This seems like a real simple newbie question but how can a person
unencode a string?  In Perl I use something like: "$part=~ s/\%([A-Fa-
f0-9]{2})/pack('C', hex($1))/seg;"

If I have a string like Word1%20Word2%20Word3 I want to get Word1
Word2 Word3.  Would also like to handle special characters like '",(){}
[] etc/