in reply to Why localize $_ in the map block?
in thread how could I use map here?

Without the local the original array is changed. Since $_ is aliased to each element the s// changes the original array. Try:

my @x = qw(foo bar CHOP_ME_OFF_foo);
my @y = @x;

my @copies = map { local $_ = $_; s/^CHOP_ME_OFF_//; $_ } @x;
my @changes = map {s/^CHOP_ME_OFF_//; $_ } @y;

print "x @x\ny @y\ncopies @copies\nchanges @changes\n";

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Re: Re: Why localize $_ in the map block?
by pike (Monk) on Feb 10, 2003 at 16:30 UTC
    Ahh, very interesting. I remember that in the Camel book where it explains the use of grep, there is an example along the lines of: 

    @subset = grep {s/x/y/} @set;

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    and it points out that this will alter the entries in @set, but it never mentions that you can avoid this by localizing $_...

    pike

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