FAQ 4.49 How do I process/modify each element of an array?

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4.49: How do I process/modify each element of an array?

Use "for"/"foreach":

for (@lines) {
s/foo/bar/; # change that word
tr/XZ/ZX/; # swap those letters
}

Here's another; let's compute spherical volumes:

for (@volumes = @radii) { # @volumes has changed parts
$_ **= 3;
$_ *= (4/3) * 3.14159; # this will be constant folded
}

which can also be done with "map()" which is made to transform one list
into another:

@volumes = map {$_ ** 3 * (4/3) * 3.14159} @radii;

If you want to do the same thing to modify the values of the hash, you
can use the "values" function. As of Perl 5.6 the values are not copied,
so if you modify $orbit (in this case), you modify the value.

for $orbit ( values %orbits ) {
($orbit **= 3) *= (4/3) * 3.14159;
}

Prior to perl 5.6 "values" returned copies of the values, so older perl
code often contains constructions such as @orbits{keys %orbits} instead
of "values %orbits" where the hash is to be modified.



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