How foreach loop in perl works with arrays in perl

Question

this program should execute three times but is executing only twice. Can anyone explain how this foreach loop will work in perl.

#!/usr/bin/perl
use strict;
use warnings;
my @arr=("sandeepr", "vijay","vikas");
for my $i( @arr)
{
    print @arr;
    my $b=pop(@arr);
    print "\n $b";
}

You are iterating over an array, so you should just print $i; You are also modifying the array you are iterating over, which is generally a bad idea and can cause unexpected results. Better to copy the array that you wish to manipulate. — xxfelixxx
– xxfelixxx, Commented Mar 18, 2018 at 4:41
Also, 1-letter variables are in general not a good idea, but specifically in perl, the variables $a and $b have a special purpose, see perldoc -f sort — xxfelixxx
– xxfelixxx, Commented Mar 18, 2018 at 4:42
if you want to print the array 3 times, you can: for (1..3) { print @arr; } — xxfelixxx
– xxfelixxx, Commented Mar 18, 2018 at 4:46

ikegami · Accepted Answer · 2018-03-19 03:00:44Z

11

perlsyn:

If any part of LIST is an array, foreach will get very confused if you add or remove elements within the loop body, for example with splice. So don't do that.

As confused as this makes Perl, you appear to be even more confused. What are trying to do? Print the elements in reverse order? If so, you could use

for my $ele (reverse @arr) {
   print("$ele\n");
}

or

for my $i (1..@arr) {
   my $ele = $arr[-$i];
   print("$ele\n");
}

or

while (@arr) {
   my $ele = pop(@arr);
   print("$ele\n");
}

edited Mar 19, 2018 at 3:00

answered Mar 18, 2018 at 4:42

ikegami

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3 Comments

rawatsandeep1989 Over a year ago

Thanks ikegami for replying. yeah you are correct i am trying to print array in reverse order ( without using inbuilt reverse function though)

Patrick Mevzek Over a year ago

@rawatsandeep1989 what is the purpose of NOT using built-ins for your need? Just to learn how it works or something else?

rawatsandeep1989 Over a year ago

@patrick Mevzek ,yes just to learn how it works. :-) what if there were no builtins.

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