Contributed by ajdelore
on Jul 21, 2003 at 23:49 UTC
Q&A
> input and output
Answer: How do I localize $_ in while loops?
contributed by ajdelore As discussed here, $_ is automatically localized
in a foreach loop. So, for example:
foreach (qw/foo bar/) {
print;
print foreach (qw/one two three/);
}
# output: fooonetwothreebaronetwothree
However, a while loop does not do this automatically:
foreach (qw/foo bar/) {
print;
my @list = qw/one two three/;
print while (shift @list);
}
# output: foofoofoofoobarbarbarbar
In order to do this, you need to explicitly localize $_
within the while loop:
foreach (qw/foo bar/) {
print;
my @list = qw/one two three/;
print while (local $_ = shift @list);
}
# output: fooonetwothreebaronetwothree
Another way to do it:
{ local $_; print while (shift @list); }
Note that you must have the local declaration
enclosed in a block with the while statement, as above.
The following example will not work:
# will not localize $_ to the while loop
local $_; print while (shift @list);
See perlop for more information. | Answer: How do I localize $_ in while loops?
contributed by Roy Johnson Please note that shift does not populate $_ by default, so ajdelore's "Another way to do it" is not. The assignment still has to be explicit. |
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