One of the things you always want to do with map is to use it to do a transformation on a list of strings.

At some point you're guaranteed to try something like this, but it won't work: 

# WRONG
@new_list_wrong = map{ s/that idiot/our esteemed leader/ } @list;

[download]
This is because s/// returns the *count* of the changes, rather than the changed string (most people agree this is a DWIM violation: this is an area where Larry blew it).

What actually works is something like this: 

@new_list_right = map{ s/that idiot/our esteemed leader/; $_ } @list;

[download]

There's still another gotcha here though, in that if you look at the original @list after doing this, you'll find that it was transformed in exactly the same way as the new list. Each item in the @list array is aliased to $_, so it can be changed by running map on it. (Of course, you knew this. But you'll still get bitten by it on occasion.)

Weirdly enough, the m// operator doesn't have the same problem as s/// does: m// does pretty much what you'd expect in list context: 

# yet another way to strip leading and trailing whitespace:
@cleaned_list = map{ m/^\s*?(\w.*?)\s*?$/ } @list;

[download]

Trivia: perl is well known for having ripped off features form shell and awk, but map was lifted from lisp.

In reply to A hint about using map by doom
in thread Turning foreach into map? by ghenry

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