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When I was learning map and grep, it helped me to see the equivalent of them in normal perl code.

my @a = map { transformation($_) } @b; # same as my @a; push @a, tranformation($_) for @b; @a

And

my @a = grep { condition($_) } @b; # same as my @a; for (@b) { push @b, $_ if condition($_); } @a

If you see yourself using one of those patterns, you can likely use map or grep instead.

And as a final note, you can use both without a block if you want to use only one expression:

my @even = grep $_ % 2 == 0, @numbers; my @odd = map $_ * 2 +1, @numbers;

In particular that allows you to write

my @numbers = grep /^[0-9]+$/, @words;

In reply to Re: map grep and sort by moritz
in thread map grep and sort by coyocanid

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