@a = map {
    # A function of $_, eg:
    $_ . ".txt"
} @a;

##</code><code>##

# Emulate grep with map
@a = map { elementShouldBeIncluded($_) ? $_ : () } @a;

# Double up the list
@a = map { ($_, $_) } @a;

##</code><code>##

@a = map {
    # Is it a dir?
    (-d $_) ?
        # Expand it (somehow) into a list of files
        turnDirIntoFilesUsingVendorProg($_)
    :
        # It's a file - pass it straight through
        $_
} @a;